Use this lua code to disable autoattack:
if (PlayerFrame.inCombat) then ClearTarget(); TargetLastTarget(); end
Don't forget also to put range better than 15 yards at your fightclass (if range is smaller than 15 yards, wrobot relaunch autoattack), you can found this option in top/left of fightclass editor, or you can also with this c# code like here line 19.