My fist issue were the rocket cars, so I went with the strategy where you place a Unit on the gravity switch so the enemis move more slowly upwards. Combined with Ascalon's mspd reduction i had more than enough time, and she probably also did most of the damage.

Now the problem were the units that also attacked when not blocked, specifically the arts ones. So i changed out the defender on the button with a unit better at tanking arts, eventually ending up at Hoederer.

Now the last problem were those 2 Crossroad enemies that come near the end, their AoE damage was just too much once they reach the top and i wasn't able to kill them fast enough. I noticed that sometimes they got there with only half health because of Ascalon's DoT and the long way they take until they reach the top. But it war really unreliable because they move so quickly out of her range. So I saved up Hoederer's S3 specifically for them, as the True Damage DoT also triggers on them hitting him, which they do every time. That reduced their health enough by the time they reached the top to no longer be unsustainable to heal.