I love the idea, it's the awesome Reprisal from 3.x and makes sure you're not forced to main-tank-- unless you're in an alliance raid, since you can't use TBN on players other than your party members. I think to synergize even more with this reimplementation, TBN should be usable on players that are not in your party, much like Clemency. In Rabanastre I (too)often see players who don't move to the other side when Hashmal does his fiery arm attack, and I wish I could use TBN to hopefully save them (but I can't because it doesn't work on alliance members). In a situation like that it could be used to prepare your Reprisal for when the boss jumps back into the arena.