Kalliope wrote:A permanent source of reliable mana gain combined with replenishment sounds pretty overpowered to me.
And I still stand by the base reasoning that the game does not need another class with a permanent pet.

Fair enough, bearing in mind that a perma-fiend could have virtually
any powers, according to where the devs want spriests to fit into the overall lvl 90 talent / spell picture, which likely will be a very different makeup than the picture we currently inhabit...
Also bear in mind when they add new end-tier talents, they often look to add abilities that shake things up and cause a real sea change to the previously accepted wisdom on the class. I would argue this is part of what makes their expansions so successful... just when we're all starting to think we've "mastered" our favorite classes, Blizzard sends us back to school.
But like I said, if you don't like the idea of having another pet class, there's not a thing wrong with that - it's like how I'd rather not see hunters with horses or stags for pets; I have no ironclad / unassailable basis for that, it's just a loose feeling, but still perfectly valid.