So its early into the game (i'm  only like 8hrs in...) and already I have 3 mages. I remember being lucky to have my two mages in DA:O and already I've got a party of Male Hawke (Rogue) and 3 Mages. I kinda feel like I should have a tank...but come on! 3 mages! Just wondering what everybody else is doing??

Mages are really sick in this game, but I still feel the need to have a tank. I'm rocking a 3 mage+Tank comp: SPOILER WARNING: Click here to reveal hidden content. Sometimes I'll switch out a damage mage for a DW rogue but I'm not too sure. 
  
My tank tactics are pretty dumb though. *sigh*

Rogue (me), Warrior (Aveline), Mage (Anders), Rogue (Varric).
 
Varric and me bring the hurt, Anders runs away from everything and spams Haste and heals, Aveline tanks stuff.
Had little problems so far, 21 hours in, on hard.

hawke: two-handed 
aveline: tank 
anders: support spells and heal 
varric: because he's cool 
23 hours for me now ( just on normal though) and im lovin it! 
 
also: 

Fenris tank, Varric rogue, Sebastian other rogue, and my Mage. 
 
Works alright

First run through I did 2 Warriors 2 Mages most of the time, although sometimes I'd switch out a warrior for a rogue.

I have a tank(Hawke), rogue(Varric), healing mage(Bethany) and tanking mage(Merrill).

" hawke: two-handed 
aveline: tank 
anders: support spells and heal 
varric: because he's cool 
23 hours for me now ( just on normal though) and im lovin it! 
 
also: 

SPOILER WARNING: Click here to reveal hidden content.

the game will totally kill off one mage at some point

"

Tank, DPS Warrior and 2 Mages. I hate having to use a rogue to unlock stuff. I modded the original dragon age to remove this limitation.

2 mages, rogue, and warrior (me). 

I played for 8 hours before coming to the realization that the mage was doing more damage with it's staff alone than I was doing with my Greatsword, so I rerolled a Mage. My party would vary, but I had at least one of each class, plus another Warrior or Mage. I then came up with a completely ineffectual build for my mage relying on the Spirit tree, so after rerolled yet again for an elemental mage.

I'm in act 3 now, and I've nearly maxed out Elemental and Force Mage, and put some point in Spirit Healer and Primal. I have Anders with me for healing, most of the time, and Aveline as my tank. I mostly use Varric as my Rogue. It's probably more suitable with Fenris since I use a lot of brittle effects, but he doesn't agree with my libertarian stance. I'll often switch out party members though.

Me - rogue - single target dps (15000-20000 crits are nice)
Veric/Anders - AoE/freezes/heals
Fenris- melee AoE / stamina buffs
 
playing on hard

It was initially Carver, Merril and Varric with my Ethan Hawke as a Mage. I eventually switched Varric for Sebastian (it takes far too long for him to become available). 
 

I did my first play-through with Merril, Anders, and either Varric or Sebastian accompanying my mele rouge Hawke

Playthrough 1 - Fenris (tank), Anders (heals), Varric (ranged rogue), me (damage mage) 
Playthrough 2 - Aveline (tank), Merril (damage mage), Anders (heals), me (ranged rogue)

I've been rolling Rebekah Hawke (2h warrior), Merrill (controller), Aveline (tank), and Varric (ranged).  I occasionally switch out Varric for Sebastian, but he hates mages and I won't have him lecturing little Merrill.

So far rocking Myself - Ranged Rogue; Beth - Damage Mage; Anders - support/healing mage and I switch between Fenris and Isabella, mainly for Isabella constant innuendos. 
 
Although I must ask is there a better healer than Anders? As he is shit compared to Awakening Anders.

Aveline for tanking, Hawke (Two Handed Rogue) and Merrill for DPS, and Anders for Healing.

Me--2h Warrior Tank 
Veric--Damage, chest unlocking. 
Anders--Healing, damage 
Merill/Bethany--Damage

I went through with  
Adahn Hawke - mage, spirit healer, almost full elemental, and some in the kinetic stuff, barrier and crushing prison 
Isabella - 'cus. Also, romanced her. 
Aveline - tank 
Varric - he's too fun. Although does too much damage too! 
I would sometimes change Varric with Merril to do her quests.  
 
Can't say I had much trouble. Hardest part by far was the Arashok, he would more or less 3 shot me :-(

Dual Daggers - Hawke 
Tank - Aveline 
Mage - Merrill 
Crossbow - Varric 
No need for a healer if you have enough restoration potions. 
 
Current play-through  
Tank - Hawke 
Dual Daggers - Isabela 
Mage - Merrill 
Crossbow - Varric 
 
And if I ever play an Archer 
Archer - Hawke 
Crossbow - Varric 
Archer - Sebastian 
Tank - Aveline

First play through I had 
 
Roland Hawke - Archer Rogue 
Aveline - Tank 
Fenris - Damage Dealer 
Anders - Healer and Elemental 
 
It worked super well because the two fighters would distract all the enemies and I would just run around the battlefield and shoot everyone in the back and generally make things explode or fill people will holes. It was awesome. 
 
Now I'm playing  
 
Jennifer Hawke - Healer + Primal Mage 
Aveline - Tank 
Varric - Controller 
Isabella - Scrapper 
 
It's working real well so far.

Well my sister had to go with the templars so now its. 
Sebastian 
Anders 
Merril 
 
Sometimes i might replace Sebastian with Ferris for his awesome abilities and tankage, but Sebastian does pretty well. I'm still pissed off that my sister was equipped with some powerful equip at the time she had to leave, the bitch.

Hawke is a male, dual-blade rogue (DISORIENTER of men). 
Main crew: 
Fenris (Tank & smasher of BRITTLE things) - got sick of Avaline judging my "rogue" decisions. Took a bit to make him a proper tank, but I think he's getting there.
Anders (Healer/Reincarnator ---maker of BRITTLE things & and exploiter of the DISSORIENTED) - He's alright. I miss Bethany, though :( Mostly keep him around 'cause I LOVED Justice in Awakenings.
Verric (Ranged Rogue & team Obscurer) - Good guy (so far)!

2h warrior Hawke
Aveline as tank
Merrill as the one who makes things explode
Varric for some dps and some crowd control
 
Most of my combat strategy involves Hawke and Aveline smacking shit up to disorient them as Merrill chain lightning's them into a form of goopy paste.

For everyone who included a tank in their composition, I want to know why?  I have found that with Fenris, dual wielding rogue hawke, varric and your a mage of choice with a healing spell I have been plowing through everything.  The fight in the deep roads took a bit of micromanagement, but everything else just gets fed into the meat grinder and destroyed.  Why tank anything when you can just DPS it down?

I've been running with a 2h war, aveline tank, merril for her primal tree (chainlighting FTW) and forst spells (brittle) and I switch out the last spot when i get bored of the party banter. Aveline and Isabel really get into it sometimes xD 
 
I'm playing on normal and i haven't found the need to have a healer, just potion chug and avoid dmg. The 60 sec cooldown on heal is bull anyway :/

Hawke is a 2-Handed DPS Oriented duder,Aveline is my tank, Anders is the healer, and Varric is the archer.I'm kinda invested in these characters, and I really feel I should just keep it safe and never change the squad. 
Also, screw Fenris.

" For everyone who included a tank in their composition, I want to know why?  I have found that with Fenris, dual wielding rogue hawke, varric and your a mage of choice with a healing spell I have been plowing through everything.  The fight in the deep roads took a bit of micromanagement, but everything else just gets fed into the meat grinder and destroyed.  Why tank anything when you can just DPS it down? "

My first party: 
 
Me (Sword & Board) 
Bethany 
Anders 
Varric 
 

Hawke (Ranged Rogue) 
Fenris 
Merrill 
Sebastian 
 
Honestly I find ranged rogues deal damage the fastest. The other two are just to distract shit while Hawke and Sebastian do most of the heavy lifting. 

" So far rocking Myself - Ranged Rogue; Beth - Damage Mage; Anders - support/healing mage and I switch between Fenris and Isabella, mainly for Isabella constant innuendos.  Although I must ask is there a better healer than Anders? As he is shit compared to Awakening Anders. "

Me - Tank
Isabella - Single Target DPS/Mage Protector
Bethany - Healer/Buffer
Merril - Blood Mage DPS
 

Hawke - 2h Warrior 
Varric - long-range rogue 
Anders - heals and elemental 
Isabela - DPS rogue 
 
Used this setup for pretty much the entire game (on normal), was absolutely fine.

First run through was: 
Hawke - mage damage dealer with a little healing at the end 
Isabella - damage 
Avaeline - tank 
Anders - healer, lover, wanted to murder him but kept him with me instead. 
 
Second run: 
Hawke - 2h warrior 
Fenris - 2h warrior 
Merrill - damage and lover 
Anders - healer 
 
Next I'm thinking: (no healer or mage which kind of worries me)
Hawke - dagger rogue 
Verric - damage 
Sabastian - damage 
Aveline or Fenris

 
Hawke - Dual Weapon / Duelist Rogue 
Varric - Auto-Leveled
Anders - Auto-Leveled
Aveline - Auto-Leveled 
 
I also played around with swapping aveline for Fenris and Varric for Sebastian.

Hawke - Two handed Sword and Reaver dps
Aveline - Sword and Shield Tank.
Varric/Isabela - Pretty much my ranged or extra high dps depending on need.
Bethany/Anders - Healing, Replaced Bethany with Anders in the Deep Road and onward to later "replace" him for Bethany in the last act

I'm not far in, but I've just picked up the last of my companions (I believe). 
I tend to roll with this as my A-team:  

Hawke (Rogue) - Damage dealer.  I use hit and run and kite to get a good angle, then go after it. 
Aveline (Tank) - Self-explanatory.  After I kite the enemies over to us, I have Aveline taunt and have them all beat up on her.  She's a tough lady.  She can take it. 
Anders (Support) - Anders is there for healing and de-buffing the enemy.  That's about it. 
Varric (Crowd Control/ Ranged Damage) - I've focused on Varric's area-of-effect talents, buffs, and de-buffs.  He'd pretty much just a ranged supporter, but he deals a ridiculous amount of damage, too. 
 
I definitely switch it up, typically throwing in Fenris in place of Aveline (he's no Tank, but he's a good controlling front-line fighter) and Merrill in place of Varric (she fulfills the ranged damage dealer role just fine).

For the Act 1, I rolled with Me (Mage), Isabela (Scrappy mcscrappy), Varric (Rogue, but I mostly had him in for the dialogue) and Carver (tank).
 
Unfortunately, circumstances..... changed, so I then decided to use Aveline as my tank. Which worked out pretty damn well in the end.

Two mages, a tank, and a rogue mainly to open locked chests and disarm traps.  If I could find gear that would allow me to unlock that crap myself then I would probably bring a dps warrior.

2 rogue 2 mage 
 
I'm basically an archer rogue, fights with admirable Legolassity. 
 
The other rogue is obviously Varric, the best character in the game, along with the now-BITCH Anders, and the Elf bitch substitute to Bethany. 
 
But wtvr I'm done with the game.

1 Warrior, 1 Rogue and 2 Mages.