I suggest Haxorus.
Drapion is a slightly bulkier Pokemon. His only weakness, ground, is shared by Manectric, who functions mainly as a offensive pivot. Drapion would not be able to reliably switch into attacks targeting Manectric. Drapion's 25% chance to land a crit, plus the 1.5x bonus of sniper could be devastating, but Haxorus is more predictable in his power.
Because Haxorus is a dragon type, there will be plenty of opportunities to switch him in, although you'll want to aim for later on in the match. The other members of your team do pretty well against fairy-types. Shaymin and Greninja can deal with anything really problematic, and an Overheat or Flamethower from Manectric will do devastating damage. They should be able to clear the way for Haxorus.
As long as Haxorus gets a chance to set up, it will destroy.
(he'll need at least one Dragon Dance under his belt, preferably two)
You already have two pretty good defensive mons, as well as two great special attackers and an offensive pivot.
Haxorus should complement your team nicely.