Torment claw does no damage if you stay away from it. You must have been punching it in the face. That'd gotta get you killed.
If you can't seem to negate damage for impossible odds, flag your people apart, so that Shiro only hits so many targets at once. Notice most anti-melee can shut him down. Blind does wonders while you cap the shrines. If you don't want blind on yourself during impossible odds, use blurred vision. Empathy, SS, SV, Spi of Failure, whatnot do wonders at all times. There are three professions that can knock stances out: use them. There are tons of damage reduction skills around: use them.
First time I played through was with my para and a dervish. It took us about 3 tries to beat the mission, and we are by no means super experts. It might be hard, but it's not outrageous: it's fine.
By the way, if you give us more specifics (profession, what you are having trouble with, etc), you get better advices.