Suggestion as to how to get people to become healers.

[Bourne_Endeavor]

Sorry, I don't think you're being entirely open with your phrasing here. You're not asking for healers to hit 85-90% of their performance potential, you're asking for them to do double duty and hit that 85-90% of dummy DPS performance - WHILE HEALING. That requires the healer to be doing a bit more than just hitting dummy damage. If you want Healers to pull double duty in that regard, then IMHO DPS (including yours) need to be in the upper 90s percent wise vs their dummy performance.

Expecting healers and tanks to contribute damage isn't doubling their duty. A healer who doesn't DPS surrenders a third of their toolkit. Both roles have a significantly simplified "rotation" because they are essentially hybrids. I'll compare my White Mage, Warrior and Dragoon openers. Notice the difference? Admittedly, I left Warrior unfinished because I have to adjust based on the group. I'll usually prep another Eye combo and setup a triple Fell Cleave but sometimes I'll need to build aggro and etc. Point was to illustrate neither healer nor tank openers involve much unless you aim for pure optimization. Dragoon, on the other hand, need to execute properly or its damage plummets. As a dedicated DPS, they must focus and refine because the less damage they do the less likely you'll clear. After all, the fights are tuned around 90% of a DPS' output. That places the bulk of the pressure to actually killing the boss on four players knowing their rotation near perfectly. If I omitted Blood of the Dragoon, well, I'm losing a massive chunk of damage. Would that be okay because "it's hard to manage?" No other job can literally stand still and do nothing except healers nor can DPS ignore a portion of their toolkit and still be considered good.

Demanding 90%+ from your DPS before they can comment about other roles contributing damage is essentially expecting they have a nearly flawless performance while tanks and healers are not held to a comparable standard.