The mob in question is melee, so they don't just "fly from offscreen". Also they are quite rare and easy to recognize. If you need to reequip all of your gear it means you're STR bugging (having items with +str sustain themselves), it would happen whenever you die regardless. Personally I've never had problems with stats as a barb because Mountain King is OP, but generally -requirements MO/jewels will help you. Other than that try farming signets of learning to add to your stats pool. Also try having +str items at a lower tier (Deadfall for example), so they give str without having to be bugged.