Ammo Sundy Exp cap - Why?

Just seems like an arbitrary limitation. If it was to prevent exploitation, they could of just used some kind of script that checks if it's the same person over and over and over for a long time. But most likely you're getting a mix of unique/new people and returning folks. They shouldn't take away incentives for supporting.

try being a repair sundy then come back.

(1xp per repair, caps before 1/3 of a single cert bar is filled)

The Medic's Heavy and the Engineer's Max is getting paid to do his job (kill everything), why should I stop getting paid to heal and res them?

At least the Medics and Engineers should go on strike until they lift the revive/heal/repair caps in at least hot-zone situations where people are getting hurt or getting killed by the second.