Fun fact: It is against the rules, and considered harassment, to kick someone from the party for performance reasons. Please don't advocate people engaging in harassment.

I also find extreme issue with the idea that off-DPS separates good healers from bad. It doesn't. Effective healing does. Maybe you feel a healer should be off-DPS'ing. Except, that's not your call. It is an individual call made by healers as they evaluate the fight and their own comfort levels. Maybe the don't know the fight wel enough, or maybe the rest of the party isn't geared enough. In that case, there is nothing to fault them on for not doing off-DPS. Additionally, if you fail a DPS check, you should be looking at your DPS, not your healer to shore up that weakness. I DPS when I feel it is safe to do so, and when I am comfortable doing so. Everyone appreciates it just as much and I don't risk anything in the process.

I find a lot of your other advice too rigid. You are trying to make rules without exception for a role where almost nothing is without exception. As a result, a lot of this advice is much less useful than you think it is.