How to make bowmaster on pvp better?

Quite well.
He was actually competitive with me and this one Evan. I don't remember who won, but it was so close to barely mean anything.
No class is simply BAD at PvP, it just takes varying levels of skill to play one well. Rather like different champions in different settings in LoL. Actually, very much like that.
Also, [MENTION=5068]Liteness[/MENTION], I've had a BM with only a Ipos weapon outdo everyone in the room, including me, a 200 BaM, a Mechanic who's one of the best PvPers in gali by far, and an I/L.
That was a FUN match.

Well, to be fair, the highest-scoring Bucc I've ever seen was ConcreteFist (?) at 1.5k points. I don't know how many points your Bucc got though. The problem with Buccs is that they have the crap mobility of Warriors (aided a little by ST, but when other classes have FJ...) while not having the high HP of them. Demo locks you into animation and it has a CD. DS is pretty much their only mob move and it doesn't hit as hard as other mob moves, although its speed isn't quite so slow anymore. They either can't or almost never stun, and have no status debuffs to inflict. All in all, they definitely are one of the lowest tiers of natural PvP capabilities.

LolEvan at PvP.
Surprised a mech is one of the best PvPers in a world anyways. Was it a match where there wasn't much running and everyone killed each other at the same spot over and over again? I can't see a BM winning a match with someone who is considered the "best PvPer" unless everyone there were morons and decided to feed points by jumping and dying on the same spot which happens sometimes in maps like Gold Richie's storage or Ariant. That or there weren't that many people, the BaM was slow, didn't use chains correctly, and was weak, and well BMs can kill mechs rather easyly on PB's map/KoC map if they know what they are doing.

Aran.

Both Evans and Arans are pretty good if you know how to play them. I can name a couple of decent ones off of the top of my head: MajesticViet, KillerCombo, Swirlled. They both thrive in mob situations.