[Vulture]

@Zonc: thanks for your detailed information. As for me I can't go with demons and undead using bowmen as 5th unit for I refuse to buy 3 talents I consider of low value if not totally useless to get to tolerance. As for Dark Commander it would take me 2 more levels to get it since I'm totally out of might runes and the handy 'easy runes for free' talent is maxed already. This includes the possibility of buying runes @ Bogacho which I already did to get my magic schools spells to a reasonable rank (for ress, sacc, target, divine armor etc). Anyways I cured Rina and she's happy with Hake as a human. I thought by myself 'I'm not going for undeads anyway, I'm a paladin and will have Dark Commander veeeery late due to lack of runes' and so didn't take an undead army into consideration.

You're certainly right about this setup being marvelous along with the talents but I'm afraid it won't work out for me at the moment since I just can't reach them/can't buy them. But that is what matters for me. My current state in the game. It is unbearable for me. I don't want to lvlup 3 or 4 levels taking 5min+ fights to the point of agony when concentration3 only delivers 2 mana per turn in order not to run to the castles grabbing reserves :/
By the way how do you restore losses on your undead troops as they can't be resurrected if I'm not mistaken ? For me it would turn out into running castles to refill which is actually what I want to avoid.

As for the tactics everything is clear. If only it was as easy as 'hit archers with archers, take melee strike units and kill archers, enemy melee is busy with demon tanks'. Those fights are piece of cake and I can win them without losses with practically every setup. My problem is for example this typical PITA enemy troop in ellinia:
3 stacks of 300-500 sprites or lake fairies each, 2 stacks of 10-23 ents, 3 stacks of 3-7 ancient ents, 2 stacks of 50 unicorns, 1 stack 8 Giants and one stack of 60 random lvl 3s.
How to take such a bunch of mobs down, especially those ignoring 'target' and lots of melee/range hybrids ? Which actually means that in this enemy troop setup they spit or melee my melee strike department down to 50% manpower (which is 2 resurrections aka 60 of 89 mana only for those, assuming target and phantom/protection spell being cast twice, once before and once after timeback on tank this means 0 mana left and numbers of ranged decimated by Giants Stomp or Ents getting them in spit range).

For a mage this would be a simple zapp 'n crack setup takin them all out quickly with Fire Rain (hello plant ents) and keeping them away with ice snakes. For me neither worked. The dryad, lake fairy and sprite (I purchased them now) setup with demoness and demon was just smashed hard leaving me with losses again. I tried a full range setup with bowmen/elves/hunters with Emeralds as tanks, supported by inquisitors and it ended up with what I said above. Turn 15+ long term fight for simple 'slightly weaker' outdoor troop just to not lose too many units.

As for availability I can't hire ancient vamps anywhere in my game having cleared all the sarcophagi and tombs so far. Castle Karmag provides ghosts and normal vamps only, same with the necromancers hut in Kordar whereas Demonis has Bone Dragons, Skelly Archs and Skells only. As for the lands of the dead I can't tell for there's a lvl 27 hero unit with 'impossible' tag blocking the first path -.-

@jwallstone: Yeah, that's actually what I came across, too when reading about these girls. The lower leadership makes up for the lower dmg range when hiring big stacks of 2k+. Below that number I'd conclude from the maths that it's practically even and prolly tending a bit towards sprites though.

A question in general is: What can I do to avoid many low stacked units to surround my tanks (if not flying) leading to the problem of additional enemy stacks ignoring the target spell because there's no space in the targets melee range ? Against fast units this always breaks my neck on the melee strikers or range/supports. Traps don't do much as I can't cast them anyway for I need any cast/turn for survival of the tank.

Another one: am I expecting too much ? Does the battle duration and difficulty (not tactic wise but mass and strength of troops wise) rise suddenly to such a huge extend when going to ellinia ? Was the impression of the first half of the game a false one ? I was used to 2-4 round mashing through any kind of troop including 'match' or 'strong' heroes even in ardent's peaks. Was that just the warm-up ? If so the general impression of the game loses in my eyes but I don't want to believe it's the game's 'fault' but want to believe it's mine.