Actually, what is most of yours take on letting a warhorse into a dungeon?
Its only usually a little taller than a human standing, and a smart horse (which a palys mount is) can usually make it through human sized doors.
In terms of avg damage, Fighters and Barbs beat palys, that's what they do, that's what they are supposed to do. Palys get to shine in certain situations, and they do it quite well. You won't be the man all the time, but you'll be the man enough to feel your time was worth it.
Also, don't underestimate the power of DR/-. 2 damage of every hit doesn't seem like much, but over the course of an adventure it can mean some seirous hp savings. At high levels, a lot of those creatures got 3 or so attacks, and since a barbs AC tends to blow, 4 to 6 less damage a round is preety nice,