Except the current form argument works even less in Pospisil's favour. Pospisil hasn't won two matches in a row this season and before today had actually lost two straight first round qualifier matches against players ranked far worse than him. He's actually in the worst form of the three at the moment (and lost to Dancevic just last month). If you want the player in the best current form to be the #2, that would be Levine as he's clearly played the best of the 3 in 2013.
Again, I ask, if he hasn't reached the heights of either Dancevic or Levine on tour and he's not playing anywhere near as well as them right now, what exactly makes him the "best" player?
Munoz is not ranked far worse than Vasek, they are ranked about the same.
His form has been pretty good, he has beaten Donskoy and played a very good match vs. Isner, his form when it's off is either because he doesn't have enough matchplay yet, or is still getting over mono, this week it looks like he may be back in form.
Wait, Levine lost to Dancevic last month too, so that must mean it should be Frank.
You really did not expect him to win his 1st match back vs. Frank did you.