I see your optajean and I call bullshit
http://www.uefa.com/newsfiles/ucl/2013/2009604_tpd.pdf
If I have to guess, the difference in the numbers, at least in part, is probably due to the corners Xavi takes. Barca corners are essentially useless, because only Pique can head the ball from corners, and he is semi-decent in that. So yeah, most of them go waste. However, looking through the numbers, it seems UEFA's numbers are just wrong.
Re-Xavi. Xavi does what he is supposed to, he dictates the pace of the game, and he dominates the possession. The problems with Barca are in other areas, because it seems Barca's attacking options other than Messi aren't doing their job. Iniesta does it, but Alexis, Cesc and Villa... not good enough really. No pace, no shooting.
However, Xavi hasn't been as dominant this season as before. And this is because of injuries. He has been missing almost 50% of games, not playing in the league and playing in Champions League. It's difficult to expect him to hit his top form, physical or otherwise, in such an injury ridden season. You may wonder why is he even playing half-fit, well, because if Xavi isn't there, Barca look worse, far worse. It has been tried and tested. No, Cesc isn't as good as a half-fit Xavi. Xavi used to be the player who runs most in Barca team, and gives crucial passes in final third, he just cannot do it when half-fit.
Xavi is a sideway passer? Haha, he is a guaranteed starter ahead of Cesc, who is supposedly the one who takes risks. It is amazing that at this day and age, people still question him. Both Barca's and Spain's best games coincide with Xavi's best games. It's not a coincidence.
Make no mistake, Spain's and Barca's TIKI TAKA WILL BE GONE when Xavi retires. All Thiago's and Cesc's of this world will not replace him. The tactics will have to change, I can predict that much. Xavi is the tiki taka guy.