Ive been dabbling in this mod a little bit myself after finishing a vanilla Harad campaign - started with the Brood of Ancalagon.
Thus far it has been alternately awesome and immensely frustrating playing an entire faction of fire breathing, naphtha drenched Mumakil. I have lost no less than three generals to freak gasoline fight accidents, and if I don't pay VERY close attention my units fry themselves when enemies get to melee range. I'm sort of fine with it if one unit shoots an an enemy in melee with a different unit of mine and roasting occurs, but it bugs me when I don't turn off fire at will fast enough and a single unit will kill over half its own members with 'friendly' fire.
Then there's the pathfinding problems inherent to being giant dragons. For every time I manage to do something awesome like this:
I have another battle in which my dragons get stuck on one another, a tree, a slightly narrow passage, or something I can't see and just sit there twitching while they die. Turning especially seems difficult compared to mumaks, I suspect because the dragons are longer nose to tail. I've also noticed that, like mumakil, dragons have trouble finishing off the last 5-20 guys in a unit as they can't get close enough together to hit the tiny men.
Don't even get me started on sieges with troops that can't fit through the gate and cant use rams, ladders, or towers. I suppose I could hire humanoid mercenaries to do that for me, but in most cases I'd rather wait out the garrison. Siege defense, however, is highly irritating. Can't move inside, can't get outside.
I've also played a few turns with the Ered Luin dwarves, and I'm slightly baffled as to how I should fight drakes/other wild creatures without taking massive casualties. The tactics I use versus other man-sized opponents don't seem to work so well.
In general I'm impressed and intrigued - excellent work, and I'm looking forward to seeing where this goes in the future