Samhain's numbers look good for me. I would keep it to marines, basic equipt predators and regular alien warriors until they feel right during test playing before going on to the the more complex stuff like praetorians or queens, for now. Armor and special tech ,like a medikit, will not be taken into account for the toughness value, they will be a whole other aspect.
@ Voodoo/Old One : Peace guys
No need to get into canon arguments, it's gonna be a small narrative driven skirmish game set in the AVP universe, so even if you separate the franchises, AVP is game
Not to talk down the predators abilities to take damage, but wasn't Wolf conveniently only hit on his mask and armored parts? I think i remember a lot of sparks flying around when he was shot.
Also in Predator, Anytime kept running when a human would have lost the leg or be crippled for life from that hit, but he tended to the wound afterwards implying it was serious and he lost a lot of blood.