Pyro: Yeah, I'm aware of that. However, two things. One, I banned Mix because I feared it would be overcentralising (due to haste, defensive buffs, and status all in one skillset). As I mentioned in my post, this proved a mistake likely, as it wouldn't have actually been as potent as I was worried about compared to things I could do anyway. Two, Encircle is only one problem with Omega's counters; another is Mustard Bomb, which does nasty unreflectable non-elemental damage, something Omega normally doesn't have and something I wasn't really prepared to deal with. And the reflecting-Search strategy makes counters a non-issue regardless.
That said, I'd still likely have used Dragon Kiss in both that fight against final Exdeath if I could, for the immnity to Maelstrom and in Exdeath's case, Doom. For Omega I'd use Mix with Mime to replace item, since it can cover MP healing in item's place. For Exdeath I'd probably use Summon + Mix? (Need the ribbon, so no Mime unless I master Dancer and Equip Ribbon carries over... no clue if it does actually.)
Re regen: Far more evil than regen, the exact same trick works with HP Leak as well, so apply HP Leak, Quick, collect victory with Omega (or ANYTHING ELSE IN THE ENTIRE GAME since nothing immunes HP Leak) It's degenerate (and slow) enough that I refuse to use it on principle. That said the regen version wouldn't actually be useful in that particular fight, as (a) it would be incredibly slow as regen would be fighting HP Leak which Omega has you constantly under (and winning, but only slowly), and (b) I had a healing skillset for free since black magic had my best damage... and just happened to also have full healing by accident due to my need for a flame shield.