Oh noez, how could I ever forget the Emerald Dragon? D:
Multiplayer I don't do too much, and that's because very few people know how to play and there is too much difficulty for me. For example, the Swarm Dragon is incredibly devastating to the Alliance and could be compared to a boss. The people who don't know how to play ignore the threat because it is too strong, and instead focus on pushing their lane, thinking that is more important. So I'm left alone with a Swarm Dragon, which is near-impossible to kill solo. I remember when I first started playing I ignored the neutral bases because I found the Serpent Wards and Obelisk Guardians too difficult to kill and I wanted to wait until I was a very high level so I could kill them. Now I understand some units are nearly immune to the attacks of the Obelisk Guardian (Light Enforcer, Elvish Champion, Emerald Crusher) and some units are quite resistant (but not immune) to attacks of Serpent Wards and can normally take the base (with help) before they die (Light Enforcer, Dark Steel Guardian). So I purchase an Elvish Champion, Light Enforcer, and two Elite Warriors with my starting resources. I definitely know new players won't purchase those things and won't use the correct units to tank, so I'm kind of on my own in multiplayer. However, I believe if more than half of the players know what they're doing, they can handle the bosses. I think if you do this, you could also balance out the addition of the superior Alliance units that spawn occasionally. By the way, maybe you could let these new bosses spawn in Insane mode in singleplayer, but maybe less frequently? Singleplayer is where I do most of my testing, and I get kind of sad that I'm missing out on a few units. (I mean, I already know that I'm missing out on many units such as the Avatar of Doom, Swarm Dragon, and Infernal Dragon, but I'd like a few more epic units to make the game more difficult and exciting.)