I feel that greninja isnt that OP, even being EV trained and wielding a life orb, it sometimes struggles to do decent damage even with surf/dark pulse on Neutral targets, (IE e16's new gym leader), Although Protean gives it STAB on its moves, helps it dodge certain attacks sometimes, but it isnt all that great, esp against tougher opponents, who are tougher than gren. They just have to tank a hit and will deal enough damage to greninja to wreck it. Also, greninja in competitive is still in OU, which is in the same tier as gengar, but IF opponents just have enough priority, greninja still is hard to sweep a team. Also in reborn, some weaker pokes are slightly buffed to make use of the field effects which will still not make greninja that much of an OP threat. Also Greninja is a starter, so in that sense, it is on the same level as the other starters.