Well Ive been getting through the game fine until now . I have to help these refuges from darkspwan but look how many there are of them . 
 

Blizzard, blizzard and blizzard. At least that's how I did it.

That's nothing in comparison to what awaits you further on in the game. I used a combination och Sleep and Waking Nightmare to deal with larger groups. If I could, I would deliberately miss one of them with Waking Nightmare so that I could use Horror on him while he was sleeping, which means instant death in many cases :D.

Indeed, I got to a point in the game where more or less the whole minimap was swarming with red. Felt like the Aliens movie, and I could just about hear my main whimper "game over, man. Game over!".   

You need to think about how to approach these battles, this isn't a game where you can just right click and get automatic kills on every fight.  You need to pause frequently, issue orders, drink potions before you're nearly dead, you need to crowd control the enemies, build your party to your play style.  I personally like flexibility and stability so I run with two tanks, a mage who can provide minimal healing, and a bard/ranger to provide crowd control or light dps, and a 5th group mate in the form of an animal.  It's worked quite well for me and on normal difficulty it's rare for me to lose a fight and those I do lose generally involve a mage or multiple mages.  To counter this I've collected and armor set that reduces spell damage by ~80%.

Be a mage with AOE spells and kill them all in a matter of seconds.

Mind Blast, cone of cold, focus dps....
 
How did you get this far in the game?

Main is a two-hand specc warrior. I run usually with Wynne, Morrigan and Liliana. All the utility. Tons of crowd control. Good dmg.
 
If somebody has too much aggro - kite the fuckers. If there are casters, either nuke 'em or cc them. Even better, do both. AoE works well on casters too, because they usually try to move out of it, during which they can't cast shit. Enough time for the rest of the gang to fuck up a the enemy non-casters.
 
You just got to have all the utility in your group and use it to the fullest. Though I got to admit. I switch to casual after dying a couple of times, then I turn normal or even hard on until the next cockblock encounter. Did most bosses on hard. They feel well balanced. It's just the fucking casters. If you aren't doing a level appropriate quest (which isn't indicated in any way) on hard and run into casters, they might oneshot your entire party - which is a fucking joke.
 
Nontheless - I love the game... and Morrigan ;P - best female videogame character ever!

That Shattering Prison spell or whatever it is SUCKS when you're on the recieving end. More often than not, if you're not full health, it's going to kill you.
 
Usually when I encounter mages (I'm a Primal mage myself (Primal? Is that right?)) I freeze/petrify/paralyse them and kill them as fast as I can while my other party members deal with the melee folk. A mage can take down your party so quick (or put them in a position where it's easy for the melee mobs to take you down fast) that it seemed worth doing to me. Chain lightning hurts.. a lot.