What is your build? Level?
My experience with cleric (but cleric in warrior guild) have been that Ark was hard up until time I got nano scalpel or sword. Gulping plenty of potions that dropped in sunken citadel helped a lot against spiders, always luring one spider only.
All got easier and easier as collected other equipment (gloves, belt, armor...). Finished Ark at lvl 22 first, than reloaded save prior to the ark and grinded a bit and finished again on lvl 26 (change in experience ladder helped as well) - was able to kill all the Forsaken in the Ark. No extra reward for that, btw.
David, if you read this - there is almost no drop if you kill all the forsaken in the ark. All I got was about 100 gold (no kidding, 2x 50) and Thuramian plate from sir Valerian:). Not much from 20+ 20lvl NPCs IMO...
Woah, someone did it? lol. Be glad the game didn't crash on you
I should add some drops I guess, but tbh it's not a fight designed to be won. Congratulations.