To get more vehicle kills: Drop the certs on getting AV mines for engineer and C4 for medic. Whenever we expect to get attacked somewhere, or are moving on to push the front, go engineer, drop 2 mines on likley approaches, go back to medic. Run up to the back of dozy tank drivers into built up areas, or flank sundies, then C4 them. Both these things are well worth the cost.
What Eso said. I play a medic a lot and I rarely get into a vehicle unless we're doing a mag push and someone needs a gunner or there's a sundy that needs filling. I'm always on the ground reviving people (not everyone gives you xp, dunno if this is a bug or not) so they can get back in the fight. Kill an enemy ESF and you get what? 500-700xp? That's the same as me having to kill 7+ dudes or rez 5+ dudes and hope they all give me xp.