It really depends on how you use your tamer. If you are getting targeted alot its usually because your not sending in the pet fast enough. Or maybe your fight AoE casters or even for PvP where resist spells is vital depending on who your fighting.
But If your just doing some good ole PvE resist shouldn't be necessary at all. Heck thats what the pets are for! Try slowing down your approach to a spawn and watch the "argo cycle" for the mobs there. They tend to attack at set intervals and if you get used to it you should be able to manage to never have arrgo on the tamer. There are a few exceptions to that but for the most part unless your hunting paragons AoE casters changelings or players it shouldnt be necessary.