Don't like it at all. Once the AI is improved after Ice, they will use Adventureres properly, and they are MEANT to be used to your advantage. The AI will also counter Archmages, even Hero ones, properly once tweaked.
Adventurerer Archmages are ONLY overpowered on a quick setting where there are problems getting a normal caster to match them. If worried about adventurer archmages in a longer game, one simply finds them and eliminates them before that tech is ever researched. But one also has plenty of their own Mages sitting around with experience to spare who will quickly promote to Archmages themselves. True, no Twincast, but that only prevents them from being COMPLETELY effective countering the Grigori Mage for Mage, it does nothing to your ability to field high movement Mounted units against them, or sending in a rush of Assassins/Shadows/Summons.
Field 30 Conjurers with Sun 2 against a Grigori Archmage Hero Meteor Twincasting crew someday, if they get within fireball range of you it is only because you decided to allow them so you could try to Dominate one for yourself.
(And by the way, I do see value in your lightning-fast and repetitive gameplay for finding problems in the game, but that is in BUGS, not BALANCE. The worthwhile thing to have come out of the Archmage issue was noticing that Elemental Resistance is broken).