You and your friends are pushing a lane. It just so happens that you get Sniped before the others. You have to retreat, even though your contribution was to get hit so that your allies could stay, instead of one of them going back. Now you get less XP.
I think that experience and gold gains should be totally shared amongst the team. This means that for killing creep X, everyone gets 1/5th of the value. Same for gold. If you want that item fast, that's fine, but your entire team pays the cost. You can see the totals.
How this would work is a series of sliders, one for each team member, that represents your share of gold and experience that you can spend. You can't shift someone else's down an below equal share, but you can move somebody else's up as a proportion of the team total, at the cost of your own. This could be directly shown as a result on-screen, i.e. you can see your available gold and experience gained to go down, or up if you're on the recieving end. In this way you can choose to delay certain Demigods from levelling, in exchange for the gain of others. I think this massively increases the number of available tactics, since you grow as a team but can choose to focus efforts how you like, in the amount you like.
Let's say you need to go back to buy an item. You could give all your experience to a teammate, because you don't need it in friendly lines, and he could give all his gold to you. Then, when you get back, you swap over. This would massively encourage team play, and be a point of uniquity for Demigod, because no other game shares in quite this fashion.
