Actually, respecing to Paragon doesn't help that much as you lose a lot of damage from Curare. Best defence is offence (poison damage will kill monsters before they hit you again). Also, unsocketing jewels with LL and resists (I hope you have them,
Jakkt) and changing them to gems will result in your char being more fragile.
My suggestion is to avoid big packs when pouncing with 50% LL and avoid staying in the melee range of such monsters as Wyrdhyena, Unseelie Lady and Trap Rat.
You should complete BRC to get a useful uberskill that will help you leech life. Also you can equip an amulet with Lightning Arena oskill instead of Doom proc and play the game that way so you always pounce withing the arena.
If you've already eaten 500 sigs, didn't Nihlathak drop any useful SU's?
(If you gathered 500 sigs by farming him, of course)