In my head, he was never between anyone and the tree. He would have been able to see Overlord in his peripheral vision (as indicated by the fact that he saw Overlord kill the mage, then immediately after fired a bolt at Drall behind the tree without any significant change of orientation).

But meh. You wouldn't be the first in this fight to take advantage of a temporal flux... And I know that wasn't your intention so you're good.