Wit doesn't really need rework.
Backstabber and Savage Sortilege need rework.
Backstabber should be a % damage increase when backstabbing, not an auto-crit.
Savage Sortilege should be 100% conversion instead of 50%.
Could also make it so crit chance above 100% increase critical damage by the % above 100.
I dunno about backstabber not critting automatically. +50% damage would make it worse off most of the time, but on crits would be devastating. Just a lot less reliable for a class that needs reliability to survive.
The crit chance above 100% increasing critical damage is an interesting idea though. Lets wits be made more versatile without getting a straight up buff (though I do think people overrate initiative a little). Of course, +1% crit damage (or chance for that matter) really don't compare to +5% overall damage of primary stats, but at least it's something useful for rogues when going for wits for initiative.
