I agree pre aquatic i had a surface spawn mob farm over water working perfectly (not stupid fast but constant drops) you cokuld work around the area and it would be always spawning. Post aquatic drowned filled the surface cap and the farm stopped entirely. I built a massive platform 12 chunks diamond (5 either side of the 2x2 chunk farm) cleared out drowned and the farm started working but slowly stopped as moving around the area loaded chunks outside the radius causing drowned spawns filling the cap again.
I have since moved to a java world till bedrock mobs become actually useful. Not to mention the combat mechanics ! Sweeping edge omg why does bedrock not have sweeping edge! I had never used java before gi ing up on bedrock and I am an instant convert. I will return when it is fixed... not before.
Blazes surviving in lava is normal. Blaze are immune to fire damage and lava doe not push mobs like water does.
Pigmen will also survive in same position
Those of you commenting regarding Java edition... this is a bedrock edition bug report NOT related to 1.13 java.
Still in 1.5.0
You are better to tp them to the void... else the entities created from the drops will lag your server... it's what I do 🙂