Holy shitballs I just made it to round 33 of Labyrinth. I'm at rank 67 now (or I will be anyway when it updates at the end of the hour).
What really did it was continually enhancing my Gram and main character (also tank) and getting lots of FB gear and maxing it. Main character has a 4 set bonus, Turq has a 2 set bonus staff/orb both maxed, Gram has 2 set bonus shield/armor at MAX/+6, Mercedes has 2 set bonus staff/orb at +0/+MAX, and Deathcrown has 2 set bonus of swords at +MAX/+6.
The real key is that Gram and my main character are practically indestructible. That allowed me to survive for a really long time on round 30. When everyone else was dead, Gram and my hero were just sitting there waiting for revive scroll cooldowns to refresh. When the cooldowns were up, I waited for the Gnarl's full screen AoE attack and after it was done I'd rez. I literally used 10 revive scrolls and 5 HP scrolls on that lab run.
31+ aren't that hard. The enemies still hit hard enough to 1-shot multiple characters, but they go down really fast. So like on 31 my Turq who has over 7000 ATK dropped her meteor, critted, and 1 shot the entire wave.
Ended with about 465k points. This should easily be enough to put in 1% for the week, although I'm currently at 67, so it looks like top 50 is still going to be out of reach unless I get some Dracos.
Funny thing is that none of my characters are even limit broken. So I've no doubt top 50 and perhaps even top 10 are possible with no dracos at all.