You're right on the percentage, accidentally copied from the QB rating.
But yet you say that we'd "win now" with a guy of Holcomb's performance level because he's better than 1/3 of the starting QB's in the league.... I'm still trying to figure out how it is that you can conclude without any doubt in your mind that Losman has at best the career potential of Ryan Leaf based on how he was thrown to the wolves last year. Holcomb brought experience at being thrown to the wolves, coupled with no false sense of security that a running game and defense were going to bail him out, and managed to eke out marginally better performance overall (however you add up the points-per-game it's not like he was lighting the scoreboard up...). It's not that I think Losman is the next Favre, it's not that I'm even convinced he is or isn't the answer. I just know he hasn't been given the chance to show who he really is. I know what Holcomb is, however, and it would be more surprising to me to see Holcomb playing better than Holcomb did last year than it would be for me to see Losman playing better than Holcomb did last year...
Look, it's an open competition now, which I support. If Holcomb wins, I'm worried, because he is not the "solution." If not, then we have something, which could admittedly be a Rob Johnson (great in practice, lousy when the bullets fly) or not, but at least you'll have a starting QB that the team will rally around, and that hopefully smarter coaching will actually support with a Roeth-type game plan that helps him get comfortable with the game...while he plays....
Again, I'm not saying that Losman is the second-coming of anything, but I'm just not ready to kick him to the curb as a bust.