You mention you've maxed out Ravager, Medic and Sentinel for Light, Hope and Fang, but how are you on their other roles? You'd really benefit from Fang's Saboteur abilities, particularly Dispel and Slow, and Light makes a decent backup (but not main) healer. At this point in the game Hope is only decent with his Synergist role and the lack of Haste really starts to hurt right around now if you're not using it a lot. My main party through most of the game was Fang, Hope and Vanille but I ended up switching Hope out for Sazh for quite awhile when the battles got too tough to keep up with otherwise. Hope's low HP also makes him vulnerable to big AoE spells.

You could also try switching your accessories to be more defensive. Dahaka has a nasty status AoE move so any resist accessories you have could be helpful, and HP+ accessories would at least help with Hope's low HP.

Other than that, keep TP handy for Renew or a summon and try using shrouds to get an early jump on him.

~DragonHeart~