- Blight has reduced effect (50%?) on Ashen Veil civs.
- Units spawned by AC events friendly to AV civs (or at least AV holy city owner).
- Enrage makes arcane and divine units to cast random spells and attack with summons rather then running somewhere and trying to melee some real combat unit. Casters are already huge pain to build and raise, please don't make using magic even more harder by wiping the work of many hundreds of turns.
- Armageddon does not affect heroes. Losing strong unit is bad, but losing a hero in a way you cannot prevent it is frustrating and makes me want to alt-f4. I spent 1 week and 800 turns fighting with all other world, with 7 civs who heavily out-teched me, and when I started to fight back AC killed me. I wish I could disable it mid-game..
I didn't know that AC 100 Apocalypse could kill heroes. AC 90 Wrath isn't supposed to be able to turn heroes insane, but I suppose I might just have been lucky that Apocalypse skipped my heroes. Saying that, it will still not affect the non-living.
I think the idea of Armageddon is that it's the end of life on Erebus. It's not the end of Good life on Erebus, it's not the triumph of Evil over Good. That's described by playing an Evil nation and winning a Conquest victory.
Armageddon is the end of days. Other than a few little differences, like the Horsemen ignoring Barbarian nations (which I think should be changed), Armageddon will destroy everybody. That's how it should be.
From your post, I have to question why you bothered with Abashi. He's a late game non-hero world unit. If you're ramping up the AC intentionally, always get the Meshabber of Dis. He's stronger than Abashi, he's available much earlier in the game and he's not affected by any of the Armageddon.
Yes, he'll cost 5000

compared to Abashi's 360

, but turn technology off once you've got Corruption of the Spirit and Infernal Pact, or otherwise once you hit Blight and keep increasing the AC. Technology will stop mattering. You'll have enough gold in your treasury to buy him in one turn, probably just in time to slaughter the Horsemen when they arrive.
Still, that's a very specialised Sheaim strategy. Remember: if you intentionally ramp the AC up, don't expect to be the one shining empire that lives in the end of days. You'll just be the last to fall, and that's how you have to play.
If Apocalypse kills heroes then I think that should be changed. The AC is designed so that it's difficult to keep it low – only the Elohim can do it. I think it could be designed better overall. Almost always increasing is fine, but as well as an unbugged Blight the Horsemen have to be rebalanced. Not useless in late game, not overpowered (or maybe leave this) in early game. To keep them non-useless they should probably arrive with an army (hint: use Sheaim Planar Gate unit types) of an appropriate level of technology.