according to arena.net's posts on how people can attain gear it's one of 3 ways.
1: Buy them with gems or gold. (this will apply to skins, lower level gear & or player created gear.)
2: Buy them with points attained from participating in events (said points cannot be traded)
3: Buy them with karma attained from how you handle quests (karma cannot be traded)
So that basically leaves people who bot with 2 options,
1: buy player created gear
2: Run a bot program smart enough to do instances, events etc...
Given how smart the AI appears to be & how active the combat is in GW2, both actions seem like they will require a much smarter BOT program then the majority of the ones out there.
That alone should cut down on the amount of people doing it & make it easier for Arena.net to ban them.