The only time an avatar will auto-attack any monster is if, and only if, the Summoner is on the top of the hate list.

The only way to be on top of the hate list is if you are cure bombing the sleeper. You shouldn't have to cure bomb the sleeper because the sleeper can cure bomb themselves. Or the WHM. If you are there as a main heal, you shouldn't have your avatar out in the first place, and your party is doomed to fail anyway.

The Auto-attack is not a problem with SE, it is a problem with the stupidity of the Summoner. Only the Summoner can fix that problem.