I did this solo with a Lock/Necro. Just DoT the tower at max range and run away. If you're quick enough you wont even aggro the adds. Each DoT cycle did ~10-15%, repeat until down and wait for the despawn.
If you're willing to die, it is quite possible with a number of two-character combinations, not only saboteurs. Just yesterday did it with a bard/necromancer combo: just hit the obelisk with everything you've got, get killed by the monsters, resurrect and wait for the monsters do de-spawn.
Soloed as a lvl 20 warrior. Like others said run in there hit it with your all. Had enough HP to make up for DPS. Died ran back and looted. Was able to loot and run.