I really like the idea of encouraging team-play with the current gold/xp system. I have a suggestion though.
Gold and XP multipliers are increased for the winning team, as usual.
Gold is gained per tick, as usual.
However, XP is gained per kill or battle participation, as in the old system.
This way the spoils go to the victor (as it should be) and experience is gained by actually participating in battle (as it should be), encouraging people to stick together.
Just a thought! Whaddya think?