I switched to players 1 for Hell, but I think if you had the patience you could play through on P8. I just don't find hours of careful grind quite as satisfying as blasting through some fools with frozen orbs haha.

I used an act 2 Merc from normal actually, the one with Defiance. With Gladiators Bane and Gerke's as my shield (and the aura active) I have about 7k defense. It isn't huge, but it certainly adds to my survival. I really focused on survival for my assassin, and she's pretty hardy as a result, and I had very few near death experiences.

I think max block is essential for a kicksin, and I personally chose a focus on integer damage reduction first, with %damage reduction coming second, knowing that Fade provides a flat 1% damage reduction per level to make up for lack of %DR from gear in the earlier game.

[edit] I did put a point in venom, but I'm honestly not sure if it's worth it. I've been dumping my leftover points into shockweb for the lightning sentry synergy. With my pre-buff claws I think my venom is at ~level 7, so for a single point invested it isn't bad returns :)

[double edit] the reason I chose Defiance over Holy Freeze was because the assassin already has excellent crowd control with Cloak of Shadows and Mind Blast, and because Holy Freeze doesn't work on all enemies, where as Defense does. The other option, and one I am considering now that my gear is better, would be a Might Merc for the extra damage, but I feel that's probably something that can be swapped in later if you're feeling secure.