I think I have 5/5 Feint, 1/5 Aura Steal, 1/5 Ass Charge, 3/5 Ambush.
But that was when acc was more important (And this gave you an acc boost when not tanking and also let you swap out acc gear for more damage gear on SA DE/Evis). It's not as relevant now.
I should probably change it to 4/5 Ass Charge 0/5 Ambush, but first I need to do all the merits after the cap increase, and finish up my war to 90 and fully merit that, so it's on hold.

tl;dr I have ambush merits, but I dont see that much worth in them. Tougher, outside abyssea content might make them worthwhile again, so they're still worth a quick mention.