Guild Wars 2

I was doing CM dungeon when we reached a tree with sniper npcs i waited for my party to engage em and i was going to support em using short bow but as soon i’m in the range of the npcs the will forget about others and start attaking me (2 hits and i’m down. i feel the thief is weak against ranged attak ) it happened twice i felt useless and i’m not a glass cannon i have 20 in Shadow Arts.
so how the aggrow works does the npc attak the player which attaked him or attak the nearst or attak the one with low health.

They tend to target the ones moving most. If you have 20 in shadow arts, go up to their face and perma blind them. They shoot slow so its possible to do that. I think they attack the squishiest. I use shaman gear and have 30 in shadow arts and they havent gone after me in forever. They usually gib my elementalist friendo though o.o