One thing I'd really like to see is things working differently based on how you choose to use them, rather than just working for one situation and then not working at al.
To make it as brief as I can, I basically mean this:
Say you have some skill. If you targeted a Demigod with it, it might do a large amount of direct damage.
Such a skill would be useless against creeps as it'd do far more damage than their health, and just be a waste.
Instead, say if it hits a demigod it just does large single target damage, but if you hit a creep it does much less damage, but it does AoE damage instead.
Another example would be a buff that if you target a friendly Demigod it boost their damage alot for a limited time, or gives them an aor fire damage attack, something like that. When targeted on creeps/troops i'd be an aoe effect buffing many of them to a smaller degree each for a limited time. A skill like that would be much less useful without such a condition. If it was just an AoE buff it could be fine on buffing creeps, but useless for Demigods. If it was a single target big buff, it'd suck on creeps since people would just quickly kill the buffed creep.
Same sort of idea with a spell that if you target allies it has one effect, enemies it has another. Such as for allies it buffs, friendlies it debufs.
Could go on and on.. It's something that'd add a lot of versatility to skills that normally wouldn't be as useful. A huge AoE blast that does lots of damage skill is clearly already useful and doesn't need such things. But I bet there are skills currently in the game that could be made better/more versatile this way. And it opens the door for thinking up new skills for Demigods being worked on..
Also, the same thing with buffs. I think it'd make sense that some aura's have different effects to Demigods that they do to troops/creeps. Like you might have an aura that is +15% damage. Well, that bonus might be low, or high for Demigods. Maybe it should remain that amount of creeps/troops, but to demigods it should be +25%, or +5%, depending on what ends up being most balanced and useful(depends how they are balanced to each other and such). I'd hope the aura's don't only effect creeps and troops. Even if the bonuses are smaller to Demigods, they'd be nice to have. Granted, it does make it harder to balnace peope choosing to stack a lot of aura's.. just means items without aura's probably would need to be better

Buffs that effect different units type differently as well.. Such as more HP to melee units while it gives more damage to ranged. Normally you wouldn't care about HP on your ranged units, but you would on your melee units. But what if you want to use a mixed army? +HP buffs would sort of force you into specializing with just using Melee units.
The same goes for Items. It'd be nice to see items that have one effect for Generals, but a different effect for Assassins.
And while I'm at it, I really hope to see Aura's that effect allies and friendlies alike, same with damaging spells.
Such as the best +damage aura in the game also effects enemies. So if enemies are in range of it, they'll do more damage. That is something i'd expect to see on the ranged demigod (regulas or whomever.) as it'd give more damage at range, but when people close in you're taking more punishment. It might be someting like 50% higher damage bonus than a +% damage aura that only effects allies, i'd imagine.
And the highest damage AoE skill, same thing.(though it shouldn't effect allies troopers and demigods for griefing reasons probably :/ Just effect your own troopers and the AI creeps.)
Same for an uber aoe heal.
They'd be considerably better than things that only effect enemies, or only allies, but they are more risky, more situational, that sort of thing.
Oh, and aura's that you turn on/off which drain mana while in use I hope are included besides the always-on one.
/edit Crud.. that wasn't brief