I’d say if you’re trying for optimal play, you’d want to minimize CON as much as you personally can get away with in PvE. CON gives you more leeway with mistakes, and you definitely don’t want to be dying in boss fights, as dead dps = no dps, but if you’re familiar with a boss’ attack patterns, you should be able to avoid taking damage almost completely. The most relevant argument I’d agree with speccing in CON is fighting ranged mobs in solo play. Homing, ranged, knock down moves are just silly, and you rack up a lot of unavoidable damage in those cases.
Not to say full CON isn’t viable in PvE, as you don’t lag behind that much from not having INT, but for eking out the highest possible damage you wouldn’t want to put all your points in CON.