For PvE I chose to go 5% crit sev, then 3% lifesteal and plan to get 10% healing. Mainly since healing is so good I can just always run first and OF everything even more than before.
I chose 3% lifesteal initially. Going from ~10% damage absorbed to 13% makes a noticeable difference. I was trying to solo epic ToS and needed every bit of the extra healing it gave me. The 5% crit severity will result in around 1-3% damage increase (depending on your build). Which is pretty small. Eventually, when I've killed Tiamat another 60 or so times, I'll get the 5% crit severity and probably the 10% control bonus.
Comments
Lifesteal is the best one but you may not be in need of it.
At any rate, you should be getting both (eventually)
There is one that is one that is 10% incoming healing bonus and one that is 10% increased control strength. I'm leaning toward control at the moment.