I agree with the first and second but not the fourth.
An army of heroes is a great unbalance thing because they are a special unit, stronger than normal ones. Dragons could be strong sometimes but they sucks at melee and against pikeman, so I dont know...
I dont think they should restrict us the way we should build an army, except for the heroes one. I think if I want to build an army with only one type of unit I should but this seems stupid since Ill have a big trade-off here, since I wont have any range attack.
If we are forced to mix our armies always then we could fall into the same problem, like in every army you will find 1x tanker, 2x range, 2x cavalry etc... Not that we will always find the same amount of type of units, but I mean we will always find the same build like tankers, rangers, cavalry and healers if we consider a full army (60). You couldnt make an army, for example, with half tankers and half healers because tankers or healers will reach their limit (maybe 16 squads per army?).