Right now, there are Exactly 3 characters that have reached floor 3 so far.
1st:
Human Cloistered Cleric 3 // Crusader1/Dread Necromancer1/Barbarian(Lion totem pounce variety, standard rage)
Abuses DMM-Persist. Commonly has 4 persisted buffs running. Initially had a huge lead on the other characters, then someone caught up...
2nd:
Dragonborn Warforged Warlock 3 // DFA 3
Uses Metabreath feats(maximize, shape) and entangling exhalation.
Uses Spiderclimb invocation for nonstandard mobility options and Summon swarm for scouting/combat.
Uses UMD for Scrolls(at first, then a half-charged Wand) of lesser Vigor.
3rd:
Neutral evil Azurin Crusader 3 // Stalwart Battlesorcerer 1 / Incarnate 2
Abuses Share soulmeld to gain extra actions. Uses Stone Power in conjunction with Steely Resolve to gain Pseudo-Fast Healing 5.
Died shortly after reaching Floor 3(because I didn't purchase enough out-of-combat healing), restarted on floor 3 and is quite successful so far.