I live on an island, and picked the wrong coast server, so with a constant 200-400ms ping, I've learned the only way I can win 1v1 is to play cheap as hell. One hit kills are your friend. I run engineer with the under-barrel grenade launcher. Even with shitty lag I can pop out, toss a grenade at the person and it either kills them in one direct hit (even with top flak armor) or misses slightly, and softens them up enough that it only takes 2 bullets to finish the job when they run around the corner. (EDIT: Just remember it has to travel 10m before it arms, otherwise it hurts about as much as a knife. Wish they'd do that with HA rockets QQ!!)Been playing for the last two weeks. It's fun and frustrating at the same time. The only non-standard weapon I have is the first VS bolt sniper rifle - everything else I use is the standard issue gun. And it sucks. I can empty damn near an entire clip as a HI, ENG, or Medic, into someone, they'll turn around and have me dead in .5 sec with 2-3 bullets. Bleh.
Plus engies make good exp repairing maxxes (double so if it's a squadmate).
Another good source of exp is overloading generators. Don't listen to people bitching that the base will flip so don't destroy anything. You get like what, 600 for destroying it, then more for repairs