I’ve suggested this in the sPVP forum already but as I thought it was a spankingly good idea, I thought I’d post here in the vain attempt someone from ANET might stumble across it! 
The downed state is great, so much better than just being killed off. The problem is the disparity between classes, giving some professions huge advantages over others.
Simple Fixes:
1) Remove damage abilities, immunity, interrupts and teleport from the downed state.
2) Have the self heal while calling for help as auto but interruptible by damage.
3) Make damaging the person doing the stomping, interrupt the stomp.
There you have it, classes downed state balanced, teamwork encouraged.
Discuss!