I liked the fourth game from the very first screenshot.
Of course, it has many flaws.
But the game was released much earlier than planned. They simply didn't have time to finish it.
What I liked:
+ Simultaneous attack
+ Superbly crafted combat system
+ No upgrades
+ 3D battlefield. In the fifth game, it's still 2D
+ Division of magic by castle
+ Giving each castle its own characteristics
+ Caravans
+ Buy all button
+ Number of spells
+ Division into mass and non-mass spells
As for the opinion about the terminator heroes, I chopped them up like firewood. Dispel + sacrifice of a weak stack + attack with the whole group, and the hero is out.