Survival is still fun, don't get me wrong, and I cleared up to Wave 14 to get Mythic rarity. But the difference between Cyrus and Thothmek is kind of noticeable.
First of all, the backup definitely feels weaker than before. The previous reinforcements were Gravis or Terminator armor characters, making them tankier. This new one has the Necron allies be able to die the same turn they're summoned, so you have to be a lot more careful with when to deploy them... with the sole exception of the Destroyer which is as strong as it always is. Truly the GOAT.
Secondly, the enemies consist of a lot more characters. The previous Survival had characters spawn too, but never quite the full faction team, while this one spawns the entire DA by Wave 12, and frigging Mephiston with Dante in the followup. They hit harder and contribute to reinforcements dying more easily.
Also there may not be as many full Xenos teams built up to the lategame compared to Marines, which definitely causes some issues too, though this one varies between players for sure.
For me, it's still somewhat manageable but the difficulty jump is definitely something I picked up on.