Thanks for input guys. I have a 20 lev mage now, and decided to get Elenhel. I have cleared first four islands (Debir, Bolo, two with pirates), can kill most of non-hero armies on Verona and Montero (except some like undead army before prison castle because they have 4 Black Dragons), or orcish-droid guardians of Umkas map, because they love to spam Astral Damage), and have access to Sheterra, Dersu, Tekron, before getting Elenhel. No Elon, so Moro will have to wait for me
My mage is somewhat weak comparing to previous games (I had 10 INT when got Elenhel on Level 18, and less than 50 mana), and enemies are somewhat stronger, especially all forms of orcs, so I'm going to experiment a bit. I've been playing HoMM5 recently, and liked their undead armies with phoenix, probably will try to do sth similar here (but without Raise Dead equivalent that could be hard).
I can't upgrade Adept's Staff to higher level still, but I'm going to eventually give that to another armor bearer (and it will give more than INT+4, hehe).
For now, I'm using Royal Snakes (still), Inquisitors, Demonologists, Paladins, Evil Beholders, Engineers and Witch Hunters (witch hunters can shackle even black dragons, hehe), depending on enemy. My pet dragon is a blue one this time, and I probably will have some green dragons in future. But while I'm willing to try orcs, I'm not going to use any Orc-only armor bearer, because I suspect that orcs will suck. There are enemies which are nasty when you fight them, but quite sucky when you have them, and I think that orcs may be such a case. For example, if I'm not mistaken, Goblin Shamans sacrifice themselves to perform their powerful Astral attack, so I'd have to forget about no-loss. And there are other specials seeming to cause loss of units.