It's incredibly obvious that some EU players are running this or something like it. They exhibit all the standard signs used in FPS gaming.
Facing normal archer:
1) You stand in the open
2) Archer aims
3) You step behind siege shield
4) Archer stops or else shoots the spot you had been standing at a second ago
Facing aimbot abuser:
1) You stand in the open
2) Archer aims
3) You step behind siege shield
4) Archer shoots anyway and the arrow matches the position of your head had there not been a siege shield there
You see this sort of thing all the time in FPS games where aimbots are more rampant. People shooting walls that another player is standing behind, etc, because the aimbot doesn't realize there's a wall in the way.