I'm pretty sure the average player can say "I'll try to use (insert ability here) more often in my rotation and see if that helps" without reaching the end of the fight and forgetting they said it.
Also, a personal parser could of course have a breakdown of how much DPS each ability added so players could notice in a second that they're forgetting to weave in a DoT or something...
It's not just progress, but feedback for when you might be forgetting something.
If a healer or tank forgets to do use a vital ability, people start dying so they'll know right then and there that something is amiss. If a DPS forgets, they may never realize it.
It would be easier to try including a personal parser in the game's UI for a week or so and see how that goes first.