i know you need over 10 k health over 490 def but how much dogde?

to tank Kara you need a bit more then 10k health, before I setted food in Kara I had 14k health, isnt needed ofcourse but just showing its easy to get good gear before you raid.

just make sure you have 490 defence, defence is also avoidence so if you have 490 defence you'll have high enough avoidence.

It's to make you uncrushable?

Uncrittable - 490 defense
Uncrushable - 102.4% chance to avoid including shield block

Not hard to reach, after that, IMO it's best to gear for health and avoidance. Gearing for more defense is more difficult and less beneficial.