Gray faced a friend, a quite powerful one, but still not a true "enemy".
Gray was powerless against Vierness in all his classic ressources until he managed to really understand what a "magic maker" really is, unlocking a new potential. This Gray is vastly more than the one who faced Mirajane on Aldoron. My god, this Gray was period his Spriggan period' shadow' self.
And seriously, as shown so far in last chapters, A Team is vastly above B Team (bar Laxus who will be seen soon).
I only consider what it was seen, nothing less. I know Mirajane gained it. I will use it in consideration when she will use it, showing us the level of her new spell by herself.
Just like I know Lucy has Merc's key but I still don't consider it until she can use it, showing the power she can exploit with it.
I am also convince that Erza hides an another enchant : all her new abilities are linked to the one she loves : Natsu & Grey (her brothers in sort), Jellal (her belove), Belserion (Dragon Slayer ability linked her mother). She considers Makarov has a father. Her ultimate spell will be link to him (Law + Nakagami ?). But without seeing it, it's still "potential".
For Elfman he used it onscreen. His brutal strength is a direct comparison to Alegria as finishers which is an incredible amp for the bro.