You can do the master quest. The master quest will probably cost you an arm and a leg, but it's worth it. It boosts your attack permanently by about 6.75%. For me the attack boost was 85, which is like having +21 dex. In addition, when your hit points are low, you'll automatically redball, which raises your resistances by 50.

Arrow Shower is a great skill for PvP in the right situation. It is tough to land all 5 arrows unless your target is stationary and you get knight noah to them. Use it on stunned or screamed targets, priests who are healing, mages who are casting, and melees who use standing combo.

Use Light Feet (LF) instead of Swift. With LF you can get out of a bad situation in a hurry, or close on someone trying to run away bravely. You can outrun everyone except other LF'd rogues. If you insist on using Swift you will be an NP donor.

Constantly keep Lupine Eyes (LE) up. With LE you and your party can see Stealth'd rogues. One thing about LE is that only the rogue who cast it gets the icon. But the rest of the party does get its effect. If another rogue in your party already has LE up, you will not be able to cast it.

Don't underestimate the value of Minor Heal (MH). A well-known sin named 0000000 says that MH is the best PvP skill in the game. A skilled rogue can make himself very difficult to kill with MH.

If you are in a party, make sure everyone has Swift. It is your #1 responsibility. An unswifted player is a sitting duck.

Carry cure curse potions (I usually lug 6 around) so you can cure debuffs. They are heavy (15 pounds) but well worth it. If you see a party member duffed (purple bar) or slowed (green bar), in particular a melee engaged in combat, stop attacking a cure the player ASAP, or they'll get knight noah.

Don't bother lugging Styx around. Most targets you Styx will either town or run away. The best uses I've found: Styxing an attacker who is close to killing a party member, or Styxing a 1920 healer so your party can finish off the healer's party.