The game is too random and unbalanced.
Some matches are so stupid, you start with one heavily blocked champion which will take you 4 turns to activate, while the enemy can potentially start with 2 champions, and activate one of them in the first round. It's basically over and you have to waste 10 minutes in an almost unwinnable game. And sometimes, a very even 30 minute match is decided by one lucky/unlucky roll of reinforcements (lol at 14 unfusable core units in late game).
Also, since mana is displayed by a picture instead of numbers, and you don't know how much mana you get for certain moves, it takes away from strategic depth as you can't exactly plan what to do and when, to get your spell ready at the moment you need it the most. Say you're Aidan and you decide to go all in with a wall attack, only to find out you're only at 98/100 mana after 3 possible free moves and one linked attack. Well, tough luck, enemy champion will kill you in the next round, which you would have survived if you opted to defend instead, which you would if you knew you would be 2 mana short.
On another note, I don't like champions being too damn strong, and the best defense being blocking them with your own, as it's faster and easier than making 6 rows of walls just to take 30 dmg anyway. Then it often becomes a war of attrition with one player constantly on the defense, losing all champs, and the second player sending waves of linked 130 dmg champs. Consequently, tier 2 units are almost never used, which is a shame since their utility is interesting, but it doesn't make up for the fact that unless they're fused, they do like 5 dmg.
If they fleshed out these issues, buffed the useless artifacts, and also added Dwarfs, Stronghold and Dark Elves, CoH(2) would be unimaginably awesome. Also, some global stats for every matchup and detailed player stats would be great, too. Too bad we'll probably never have any of this.