Something i found of interest, Quoted from Castle.
"Stalkers Assassination attacks have been modified for PvE use. The damage scalar used for the critical portion has been broken into two parts. The first part, which operates the same as the original Critical, is now 2/3rds its previous value. The second part, however, does 10% of the targets maximum health, prior to resistances. Against underlings and minions, this results in slightly lower overall damage. Against Lieutenants, the damage is roughly equivalent. In all other cases, the overall damage output should be significantly increased."
Even though they are working on this modification atm they say that it will not be likely to be ready for the next patch which is due sometime this week.