I have a sorc 441, Frostmetal 0 and daylight accessories, tier 3 etchings from IoD, all glyphs etc. I have a valk, priest and gunner too and don't have any problem with Pit of Petrax on them (all have hp regen abilities though). I struggle a bit on the sorc in that I have to use a valk health pot (you can't buy these in game can you?) most of the time, I just take too much damage. I save my mana shield for when the red balls stop dropping (don't last as long on the ground now), but it doesn't last long, I have tried kiting him but he always seems to get sneaky hits on me that take a load of damage and it makes the fight last ages, most of the time I'm not getting hit by his fire attack, but often get some sort of debuff that eats my health.
Anyone have any tips?