If your wanting to use that base, every job other than WHM in this game is severely overpowered.
Exactly. Speaking about how something is overpowered in a limited situation is nothing but silly. People insist on bringing up extreme cases like it were something that were happening constantly. As we all know DRKs with 2 hours and krakens are not exactly weak, but only fools bring it up as an argument against changing the DRK job in any way.
As I see it the only time a job possibly could be called overpowered, is when it is the main choice for the majority of the game. Which actually means the list of overpowered jobs are RDM, WHM, BRD, WAR, PLD, SAM, BLM more or less.
But again, it is a moot point arguing about what is overpowering and what isn't. Much better to discuss what makes the none-overpowered sessions of the game more fair. In this case not losing MP and able to rest with an idle avatar.
I don't see how resting with an avatar out is the same as a BLM resting with a slept mob. The way I always saw it was the avatar didn't want to be there and was resisting. And the SMN was using it's MP and "concentration" to keep the avatar in check.
That would be from a story perspective. Do also note that from a story perspective summoning Fenrir kills you, as well as he can fend off 5+ King Behemoths on its own.
The comparison to BLM btw is about result and effect. In reality a BLM sleeping a mob and then resting is MORE unbalanced than a SMN resting with their avatar NOT engaged.
Secondly, say they get rid of perpetuation cost; what happens to all that -perp gear? It'd become completely useless unless they changed it. And I'm scared of the idea of that much auto-refresh gear for SMN. You'd be main healing for the rest of your life.
That is quite off topic since there is no discussion about removing perpetuation during battle, only when not fighting.