I don't know if any of you have played Savage2, but whenever you debuffed/hexed an enemy it would die you'd get gold.
If you buffed someone and they killed someone, you'd get gold.
I think this would be perfect to have in Demigod, and give good incentive for helping your teamates kill and NOT trying to steal their kills.
Also, this should effect NPC creeps too IMO.
Say you have an AoE +15% damage buff. If an ally kills, you should get 7% of the gold for that kill(NOT taking away from them, just adding more. So if it was 25gold normally, they get 25 and you 2 gold.)
Or a single target buff that oh say, lights targets weapon on fire, making do more damage, blah blah. Say that gives a set amount of extra gold for kill based on a guesstamation of what % increase that'd usually be. So say some +150 damage(just for example, don't know hwo mcuh damage things would usually do) would give you 10 gold whenever someone kills with it. It is probably much more benefitial to buff allies ally with that since they'd get more kills with it than you.
Similarly, healing should give gold.. I think that one is probably a given and i'd be surprised if that wasn't considered already.
Also, in DotA the NPC creeps often "steal" kills. Having AoE aura's and buffs giving you gold when they kill would help a bit.