Nah he's not. He's been poor recently because he's been thrust in and out of the team and expected to form a defensive unit with whoever he's been paired up with which is hard for any defender to do. Remember how poor Monreal looked when he was only given the odd game here and there when he first joined, and yet he's our most consistent player right now. If he's given a run of games (which hopefully will happen as I personally want Bellerin to move forward until Ox/Ramsey gets fit) I think we'll see the best of him again.
Bear in mind that he's a French international RB, who was preferred over Sagna by France at the world cup. In a way I kind of feel sorry for him - he finally got his move to a top club right when he's hitting his peak years but a few unfortunate injuries (one of them thanks to a needless shove by Stoke thug) and the emergence of a truly world class fullback and our best one since Cashley has ruined his career here so far.