overread: Sadly Disciples 3 was built on the same game engine and design as Heros of Might and Magic V - as such it sapped a lot of hte original content from Disciples 2 and 1 that we were used to (namely having more than one home city). However that said Disciples 1 and 2 still had the same balance problem that 3 has; that of being a turn based strategy game, but where one is forced into the use of a single superparty for most missions (esp in the campaign play).
I actually think the 3rd has done more to try and break that pattern, however it still stands that your main hero needs to kill mostly everything on a very large map before you want to progress (simply to get the exp for the levels). And it also stands that if you lose your single super party chances are you've lost the game unless you're a mage and can magic out the opponents main party.
I've never minded the one main party thing personally. I've always thought of Disciples as an RPG with strategy elements. Heroes of Might and Magic (I like 3 in particular) is a strategy game with RPG elements.
Magic in Disciples 2 was pretty awesome in single player. It completely unbalanced multiplayer though.
overread: As for the new title (note I've never ever been a big fan of stand alone expansion packs - mostly cause they never add quite enough to make you want to buy them full price when you already own the core game) you get the Undead Hoards and a long single campaign game for them. You also get them and the other three armies (humans, wood elves and demons) in the skirmishing games. The game also addresses a lot of the balancing issues from the original and, from what I understand, its much earlier Russian release was met with a good report.
If it's only the one campaign, I'll pass. Maybe a gold version will come out with Renaissance and Resurrection merged.