1) I like Imps more, I won't argue... I only use Fiends to drink mana.
2) Before, Demons were just meat... now they are useful meat... which can also fight.
3) The new hounds are definitely cooler... but what if the opponent doesn't place troops in a crowd, but in a line? Besides, their attack is lower than that of another upgrade.
4) Temptresses are also not very good... but they won't replace Chain Demons. It's better to take this upgrade against your own demon brothers.
5) Horses... well, maybe they are better... but the damage from their "fire" is not very impressive.
6) And here it depends on personal preference... in general, I think Imps + Cave Lords = we'll make life difficult for the enemy... the new upgrade is against low-level creatures (especially against Necromancers...), and the old one is the opposite.
7) Damn, if Domains had teleportation across the entire battlefield :D and could teleport Elven Archers or Druids there... well, that would be cheating... besides, it would cost a turn to teleport.
Added 2 minutes later
By the way, regarding Archdevils... they should improve this ability in a future patch... for example, teleport a creature to themselves (same distance) and attack without the enemy's resistance... or teleport a friendly creature to themselves, and the teleported creature receives a bonus to initiative, and the Archdevil only spends half a turn