Managed to get to the roof, thanks to
@Kyronix. Took 3 tamers, using my usual tactics. One had a White Wyrm, one a fire beetle, and one a giant beetle.
Ozymandias: I did have 3 pets on him, but the volume of spawn was greater than anything else. It's nothing to worry about though, so I just went about my business until someone in vent announced a dungeon fight.
Anon: Had one tamer attacking it with Fire Beetle. White Wyrm and Giant Beetle tamers were dealing with the summoned spawn.
Virtuebane: Didn't see him before the aforementioned dungeon fight. But I would guess using an approach similar to what I did for Anon will work, in addition to keeping him e-fielded...and healing my pets.
Juo'nar: For a single person this is ridiculous (as is currently the case now), but for a group it won't be too bad; my usual approach with multiple clients is keeping the other tamers far out of range, command pets to guard, friend them to one tamer, then "all kill" - the other two will aggro as soon as he uses an AoE. The spawn can be a bit hard to handle (the tamer will likely die to all of the AoE's, and Skeletal Dragons do have their 3x dmg on pets ability), but I would recommend a dexer with Whirlwind to deal with it.
Next time I go down I'll bring a Sampire just for the Lich.