With Scholars, I've had trouble with some who are probably thinking they are actively healing by spamming Physick or Adlo on me, while completely ignoring their actual main heals Excog and Sacred Soil (and Lustrate if needed), not using the fairy abilities or Recitation and Emergency Tactics. These are usually also the Scholars who complain they don't have time to DPS because they are (making themselves) so busy healing. Same thing with WHMs who are scared to Holy and then we're missing all the DPS and mitigation from it and they'll be struggling with healing.
From the healer perspective, I've also experienced the 'waiting for the tank to use their invulnerability, but they were never going to' situation. There are apparently still some tanks trying to save those for some mystical 'emergencies' that would somehow be worse than the first pull of Academy without your biggest cooldowns. And then there are those tanks who are using them at the beginning of the pull, when the WHM is still doing nothing but their Holy spam, so it goes to waste.