is it me or is the combat inconsistent? like sometimes they target my monsters and some times they skip them and target me
Yes that's not just you 😊 enemies will choose between you or your summons to attack - if you have a summon with the "targeted" status, then enemies will only attack that summon.
so a no damage run is basically all luck based
If you are trying a 'No Damage run', using Defense is the best way to go to not take any damage