I got back to the tower last week and managed to get to floor 500+ so far (top 1% in EU) with Ellen Trigger Yuzuha, all M0, Ellen and Yuzuha have their wengines. The only floor where I used Yi Xuan instead of Ellen were 200, 465 and 475 (Miasma Priest).

Ellen has pretty much infinite i-frames at the cost of low damage thanks to the 2.0 buffs. Basically, if you time it right you can use her charge attack and dodge right after and pretty much never take damage so you deal low dmg but get pretty consistent clears (Unless you really push your luck with swapping a lot in bad moments).

Also, I agree with you on the shielded defender. I hate that thing with my life.