Vist sets up at D33. Vists's all day buffs include a Chain Greater Magic Weapon CL21 (affected by God of Thunder for +1d6 extra damage), Mage Armor, Craft Magic Tattoo (+CL), See Invisibility, Heart of Air/Water/Earth/Fire, Elemental Body, and Heart of Stone. Everything is at CL 22 except the Craft Magic Tattoo which is 21. The DC to dispel any of that is 26 (25 for CMT) due to Ring of Enduring Arcana.
I also have a Greater Mighty Wallop memorized for some reason. If nobody wants it, I'll swap it out for something else.
While we have a nice built in choke point at the door, I'd suggest we don't neglect the idea that something might come through the walls.