Healing should, at the very least, be severely reduced in combat. Given the notion of reduced TTK, healing in combat could be capped at e.g. 10% of health every second and would get completely cancelled if the player got shot.
The current meta of running around, shooting heals around, dumping support stations and having 40% instantheal available almost all the time absolutely has to be done with. There is merit to all of the "baiting" and movement, but it ultimately creates an extremely chaotic and unpleasant experience to at least one party involved.