Have been running expert Rust with my max siren lead, 2 rippers (light/dark), rainbow keeper, machine golem mkII and a chaos dragon friend (dmg reduction).
It is the easiest expert level I have done so far playing. With this team - can finish it in less then 10 minutes.
I am tempted to try the higher level but worry about burning the stamina for failure.
I have run the dungeon 4x today and have had 2 lil chaos drop and 1 succubus drop. I fed the little chaos to each other but didn't get the skill up.
The succubus is my second since starting to play, the first I have leveled to lilth (4* currently).
seems like it would be nice to have 3 poisoners for the mask dungeons so I'm not going to feed the succubus unless I have at least 2 more drop over the next week. I don't see doing any other dungeon until this expires - 8.5k exp each run is pretty nice for the chance to get the lil choas dragons, the poisoners and less important the mechdragon.
now I just have to wait 130 more minutes to be able to run the dungeon again.