You know what's totally awesome? Getting into a boss fight and putting the controller down because you think it's one of those fights you are supposed to lose.
 
I'm horribly stuck fighting Barthandelus Volume II in chapter 11. 
 
I went into this battle originally with Lightning, Fang and Vanille, but after getting murdered a few times I switched Fang out for Hope just so I could have two healers at hand. The problem with with having two healers is that I only have one attacker, which means that the inevitable doom spell will be the end of me.
 
The problem is that one healer doesn't work as well, because the random lasers Barthandelus shoots me with do a lot of damage very quickly. I'd like to buff up but I need a healer to heal everybody from the barrage of attacks, so there's no time for those. If I get buffs ready, Barthandelus just dispels them off.
 
I'm stuck in an infinite loop of getting absolutely nothing done. My current record is getting him down to JUST 2,3 million hp. I achieve that by having two healers on most of the time and slowling chipping away at it's life with Lightning. That strategy isn't going to work, because I assume there's a Doom spell in the mix there somewhere eventually.
 
:(
 
Any tips of any kind would be very welcome. My current party is Lightning, Hope and Vanille, but since Final Fantasy XIII is totally awesome and levels up the characters you are not using as well, I could easily switch people out if anybody's foolproof strategy involves some other character.

That's just wrong. As wrong as it can be, and I doubt the guide told you to play that way, and if it did, you should throw it out the window. Have your dog take a shit on it. It's no wonder why you don't enjoy the game and keep failing, with that setup. First rule of thumb is: never use SEN. Only on specific end-game missions will you need it. So, this is how you should roll in most situations (may vary a bit depending on your setup)

RAV/RAV/COM - For staggering

RAV/COM/COM - Damage once the enemy is staggered

COM/SYN/SAB - For applying buffs/debuffs in the beginning of the fight and once they run out.

MED/RAV/COM - For light healing, while you keep staggering

MED/MED/COM - Powerful healing for dangerous situations. Depending on your setup, it can be MED/COM/SEN or MED/MED/SEN too, I guess.

The last one is up to you. It could be something like RAV/COM/SAB for reapplying debuffs without having to pull in a Synergist.

That's just wrong. As wrong as it can be, and I doubt the guide told you to play that way, and if it did, you should throw it out the window. Have your dog take a shit on it. It's no wonder why you don't enjoy the game and keep failing, with that setup. First rule of thumb is: never use SEN. Only on specific end-game missions will you need it. So, this is how you should roll in most situations (may vary a bit depending on your setup)

RAV/RAV/COM - For staggering

RAV/COM/COM - Damage once the enemy is staggered

COM/SYN/SAB - For applying buffs/debuffs in the beginning of the fight and once they run out.

MED/RAV/COM - For light healing, while you keep staggering

MED/MED/COM - Powerful healing for dangerous situations. Depending on your setup, it can be MED/COM/SEN or MED/MED/SEN too, I guess.

The last one is up to you. It could be something like RAV/COM/SAB for reapplying debuffs without having to pull in a Synergist.

http://www.youtube.com/watch?v=mV8lsqqQp2Y BA-BOOM It's been awhile since I played FF13 and didn't remember alot of the fight, so hope this helps. If I remember correctly though, I had like 5k or 6k health for each character because they were almost maxed out and had all health rings. With that, I just used Sazh to get some buffs, and used a Commando/Ravager/Ravager combo on him. Once he was staggered, I used a Commando/Commando/Ravager combo on him. Between that, I used 2 healers and a commando to keep the stagger up. If you're at the 3k health area, use the video. I failed once because I spent to much time healing and the doom ability killed me.

I went into this battle originally with Lightning, Fang and Vanille, but after getting murdered a few times I switched Fang out for Hope just so I could have two healers at hand. The problem with with having two healers is that I only have one attacker, which means that the inevitable doom spell will be the end of me. 

@Ventilaator said:

I went into this battle originally with Lightning, Fang and Vanille, but after getting murdered a few times I switched Fang out for Hope just so I could have two healers at hand. The problem with with having two healers is that I only have one attacker, which means that the inevitable doom spell will be the end of me. 

I do hope that by this point in the game you realize that each character can fill more than one role, yes? Having Hope and Vanille still means you've got 2 Ravagers with you in addition to a buffer and a debuffer.