When it comes to 2 slot Najasaurus, i'll farm for one with 190+ DEX (190 is movement speed cap) and 180+ Resist when wild (tamed Resist is 90% of it's wild Resist). The FWW+PB Najasaurus is probably the greatest AoE pet in game. The complete Poison Immunity means you'll always be able to heal them, even when they're surrounded by Poison spamming mobs, except when the rare Mortal Strike creature is on them (like a Dimetrosaurus).