So you assume that Fairy Tail is copying One Piece?

Have you read much manga before? Or do you just watch AMV's and read Wiki's, because if you've read a few manga's you'd see all the cut corners they make to reduce time, which also helps animation studio's reduce production costs by not having to animate as much.
In case you haven't noticed, combat-heavy scenes take a long time to animate and a few times small studio's have collapsed while animating battle scenes because of poor planning and money managing.