I only play DPS. And when im going, im usually tunnel-vision DPS. Im looking at my cast bar(and the bosses too if they have specific attacks i need to watch out for), im looking at my buff timers and cooldowns, im looking at the ground near my feet to know if i need to dodge anything, im looking at the aggro gauge to know if/when to dump hate, if a lot of reses are going out im looking at the healers mana bar to know if they need an infusion, im looking at the LB gauge to see if i need to use it(though as a BLM its not usually my job) and im looking at the bosses health to know how close we are. With all that to focus on, im not looking too closely at what the rest of the party is doing. If im drawing aggro(even though ive used both my hate reduction skills) then ill see if the tank is using their stance(or if im just severely outgearing them). If the mob groups are taking too long to die, i might try to keep an eye on the other DPS to see what theyre doing - though the odds of me knowing their class well enough to critique are low so unless its obvious im not liable to say anything. If we all die to what should be an easy fight more then once, then and only then might i try to watch the healers actions.
So with that said, scrutinizing and criticizing healers is SUPER low on my checklist. About the only thing a healer can do to really set me off is to showily do nothing. If the incoming damage is low and youve gotten bored enough that you feel like dancing, or jumping around the room like a kangaroo then you are the problem. If the fight is so intense that you cant risk being unable to heal for the next 3 seconds or we'll all die, then just stand there looking intense and i swear i will never notice you. Ive got too many other things to look at(and again, the intense fight youd be healing a lot so even if i did look id see you keeping us alive and be glad you had my back). But for the dancing kangaroo healers(and no this isnt an exaggeration - i have seen it more then once) please stop it. Or play something else. Maybe youd enjoy bard.