I like it. It will give hardcore PvEers a way to help out their hardcore PvP friends. Since Yoshida's said elsewhere (can't find the quote) that he wants PvP to be on-world, the people you're summoning Ifrit against had their chance to stop you by interfering with your binding party in the first place.

I just hope that the areas where Primals are fought to be bound is PvP-contestable so that it's more of a contest than a race - and also give hardcore PvPers a way to help out their PvE friends.

As for PvE content - if killing a boss once by throwing a Primal at it gets you one kill's worth of loot at the cost of a Primal Summon, I don't see the problem. Nobody ever just kills a boss once and calls it good, and anyone who's keeping track of the "competition" will just have separate ladders for "Killed it with a primal" vs. "Killed it without a primal."