Challenges are more about skill, not necessarily difficulty. The difficulty is up to the game to decide. So enemies healing you are the game's conditions. You could leave a disclaimer saying, "you'll notice that enemies heal and that's not part of the challenge."

I found this with games, also. I don't know if you've heard of "cheese" but in a strategy game I played, it was looked down on. Some strategies were obvious cheesing, trying to win by cheap tactics instead of outplaying and outskilling the opponent. But then I used to worry what was cheesing the entire match, and if so, my win might not be that significant.

Do your challenges anyway. OCD has elevated the symbolism of what it means to do things authentically, and it's added social stigmas to it (will it be honest, etc.) Honesty is fine, the occasional disclaimer or careful wording is fine, but OCD is taking this to ridiculous levels.