You're a thief, and that changes the answer.
As a 30 thief, don't worry about it, but as a thief, keep it in mind once you hit 40. By the time you hit 60, you will want to have equipment swaps. They don't have to be expensive, but they're almost necessary to help correct some imbalances the game throws thieves. Unless SE boosts thieves, multiple equipment swaps will be the standard for even average play.
Swaps you will want as a pickup party thief:
Melee set--I boost acc, att, triple attack, and criticals
SA set--dex primary, attack secondary, str tertiary emphasis
TA set--agi primary, att secondary, str tertiary emphasis
SATA set--dex->agi->att->str->
WS set to modify the above--DE will require acc modification to the above macros because it is a 5-hitter, SB won't usually since it is only 2, and the first is the most powerful and never misses.
Steal set--the bane of mages trying to cast on you in bibiki
I'd also recommend a pulling set with ranged attack and bolts if you can find the time to level your mark (because you can't keep it leveled while leveling without hurting the team).
At the end of your career you'll have one more set to build--your soloing set. Emphasis on evasion.
Bottom line is that a good thief accomodates their pickup parties to the best of their abilities. And because your power is governed by more variability than any other meleer, you have to be equipped for whatever your pickup party needs you to do, whether it be to sa/ta the tank. Ta the tank. SaWS on your own, etc. If a mob turns from the tank, you should be ready with a sa/ta/ws. But if your partner fails to turn the mob, a good thief will mash their ta-only macro, then use their weaponskill, mash their SA only macro, run around, and sneak attack. In that situation, equipment swaps can literally mean the difference between hitting a taws with +20-something agility buff and a sa followup with +30-something dexterity...or simply hitting a pretty poorly-buffed ta/ws with worthless dex thrown in there while you outright blew your entire sneak attack.