Ramping up difficulty doesn't mean they should go against the percentages for effects of attacks.

I do agree that to make the opponents more difficult they should use items during the battle and not use stupid attacks (example: opponent's geodude keeps using defense curl even though I'm attacking with a special move) during the battle. The opponents should even switch pokemon out to get the upper hand during the battle and also have more pokemon in their party that don't go by the 'more pokemon you have the lower all their levels are' rule. I also think if there should be a difficult option, the player shouldn't be told what pokemon the opponent is sending out.