The current reward system is retarded, it is rewarding for players who use low tier gear, and punishing for people who use medium/heavy.
What I`m suggesting is pretty simple, remove the reward cap, and align the reward according to the total gear cost.
For example if you have 30 players online at the same time, with a total gear cost of 700k gold, then the reward should be something like 10% of the total cost as an XP reward, and 3~ % gold reward.
Of course the numbers maybe a bit exagerated, but I think you get the idea.