What is your opinion about Heroes IV?

The main thing is that the fourth is better than all!

Not an indisputable statement, to put it mildly :p
In the fourth game, there don't seem to be any random cards. Only fixed maps (correct me if I'm wrong, it's been a while since I played). In the third game, even when playing with fixed maps, you don't have to restart very often. And the offline mode is better in the third game :p