If you have as much experience as you claim, then you know pets don't have the health to absorb big hits regardless of resists, and that being able to replace them quickly is only useful if the enemy doesn't glance in their direction before you get them re-buffed.
Masterminds can be strong as long as the encounter plays to their strengths. Fortunately most encounters in CoH do that, being made of packs of enemies that hit lightly enough a pet can survive. But the ones that don't, REALLY don't. When an AV (or anything you can't shut down with the limited CC options available to a MM) has a big aoe, only sheer luck will leave any pets standing when it goes off. (And only turning the speakers down will save you from permanent hearing damage, but that's an entirely different category of stupid design.)