I dont know why you got stuck on floor 69 where you have Warlord. Which basically shutsdown every skill of your enemies.
I am on floor 69 of hard now and I just auto the whole floor with Lyssandra, Warlord, Psylar, Arbiter and Venus.
My team is focus on CC and more turn cycling with Lyssandra, Warlord and Psylar. Arbiter is for more turn cycling and Venus is my dps. Arbiter and Venus is my team is flexible.
As of now the team that I theory craft since day 1 of doom tower aanouncement is still working.
Focus on CC and turnmeter manipulation rather than damage.
To those who have no Warlord, an AOE provoke champion should work just fine.
In stages where there are bombs, I use Mauselum Mage instead of Arbiter for aoe cleanse. In stages where there are Tormins, Doompriest works fine although your champions can get frozen again when Doompriest puts buff.
And to those who don't have Lyssandra, any champion with aoe stun like Scyl can help too.
I will see tomorrow if my team can still work in stages 70+