OK so let's start...
There are two problems that I'd really like to see handled pretty soon, because I believe these are the biggest problems in the game.
The first one is simple: Health stacking. It's been mentioned over and over again, but nothing has been done about it. Apart from the incredible durability a high health grants a demigod, the other big peeve is it's linear scaling. Demigods that are supposed to be balanced by a lower than normal HP get as much benefit from it as everyone else. Unclean Beast is, for example, supposed to have a good 20% lower HP than the rest, but he frequently ends up with the highest in the game, because he is fast, has a great attack, and super powerful skills. On the other hand we have the Rook, who is supposed to be the slow tank demigod. Thing is, if he goes for a high health, he becomes a slow, useless, lumbering hulk of a target. His greatest weakness is his low speed, and guess what... The speed enhancing items in the game are all % based!
That should be applied to both Health and Mana items. A fixed % based off the demigod's own base health at a certain level, taking the +stats skill into account(to buff that little bugger a tad). Something like 10% would replace 400 items, 20% would replace 800 items etc.
The second one is more involved, as it is an effect that several demigods have in several skills. Stun. Please note that the demigods with the most readily available or most potent stuns available are currently the most powerful ones, Erebus with his huge AoE long duration stun, UB with his stupidly powerful instant 2s stun, Oak and his instant and low recharge line stun... Rook and Sedna seem to be kind of in the lower-high tier with their respective stuns, but have problems of their own.
Thing is, these need to be worked on on a case-by-case basis, no one-size-fits-all. I think the Stun should be removed from UB's grasp, replaced with a severe movement and regen penalty. That's one example.
Once we get these two sorted, we can start working on Generals, Minions, Items favoring Generals over Assassins etc.