1. As listed in the patch notes, the corner pillars have been replaced with water fountains. The old water fountains have been removed. You can no longer trap Vanaduke against objects.

2. You can no longer reliable trap zombies against walls to make them inactive. You can still avoid slag guard spawns if you do not kill all the zombies, but since the zombies will be walking around instead of against a wall, you need to be careful not to shoot them.

3. The lava tile limit appears to have been increased in phase 3 to phase 5 levels. You'll have more lava to deal with sooner. There is still a cap to the amount of lava allowed, so it's not a big change.

4. The shivermist range change is just large enough to make it difficult to spam freeze on him in P5

Judging from the skill level I generally see in PUGs and even my own guild, I'm guessing most players will no longer be able to reliably kill him.