We typically play 2 player Apprentice/Huntress, or 3 player Apprentice/Huntress/Squire (25-30+). We have so far attempted this challenge several times, with the same result. At first it is fairly easy to keep the ogre safe by moving traps and focusing DPS on nearby enemies. Towards the last few waves, the big idiot starts walking right into the fray of massive amounts of enemies and despite best attempts he always drops when we have only a few waves left. Early in the regular game I had these same type of frustrations and found that what we lacked was more strategy than skill. So what is the most effective strategy with the ogre?
The best strategy I have found to work would be to place gas traps just outside the spawn doors, and blockades at the top of each of the three corresponding first flights of stairs. Place your most powerful character's towers just outside of an ogre's reach. From there, simply maintain and upgrade your defenses to prevent any enemies from getting past.
Here's a guide that explains in detail a few strategies on how to beat the challenge: