i only have play the expansion for 2 hours but i think i gonna give my first impressions.

Positive points:

First, the game looks a little bit better. Graphics are enhanced on the overrall and that's good.

Tactical battle start to feel better with more stategy. The swarm mechanism is the main addition to the game and seems to work. I hope more mechanism of that type will come later but it's a good beginning.

It's a nice addition to give a few troops at the beginning. It makes possible to put larger group of monster at the beginning.

dissapointing points:

heroes abilities at the creation haven't been modified/improved. I think some new skills could have been implemented at it creation since the expansion focus on heroes. Interface should have been rebuild to match those improvements

No possibility to create the starting troops that will begin with the heroe. I really would have like to be able to choose among some troops and it could have give a faction some nice special trait. ( ex: recruit spider/beast as beginning troops )

Heroes specialisation feel mostly "empty". Really too much "+1attack", "+1init", etc, and not enough special skills/abilities to use on the world map or in combat. ( unless you choose the mage, you get only 2 or 3 special abilites and they aren't all awesome ). Random skills selection have been remove and skills have been organized in trees with exact about the same skills as before. Only little improvement, mainly interface rebuild.

I really hope you have some others things coming because i was really disappointed by the lack of interest in heroes building using "boring" and "unrewarding" skills trees. I don't want to have to level up a hero to get 30 +1bonus in stats and 2 or 3 "special" litlle skills.

I hope i am wrong but legendary heroes feel like somethign between a big patch and a real expansion. It really lack of either ambition or ressources ( or both ) to really improve the game.

But still those impression are based on a beta so let's wait/play and see.