Major whole fight ruining game breaking exploitish spoiler:
Hide Astarion behind before engaging him and pass persuasion that you will betray Astarion.
Then make sure he doesn't see Astarion.
Cast Daylight Enchant Item on him and he doesn't turn hostile.
Bug - Both daylight options say enchant item, only the right one is, the left one puts it on the ground and makes him hostile.
O I remembered to turn off HDR for once before recording it so the colours aren't all faded finally.
