Im a healer main at 3.5k rating pushing mostly solo in pug groups. This season i play mw and disc.
This is not meant as a whiny post about dps players being garbage. I only want to give some advice!
Tl;dr: use your defensive before you are about to take dmg. Not after you already took the dmg.
I notice alot of dps players are kind of clueless on when to use their defensive this season, more so than previous seasons. Imo this is mainly because of two reasons
1: weakauras are gone (ish)
2: damage profile this season is a bit different
This season they changes the dmg output of the dungeons from big one shot burst to sustained / ticking / pulsating dmg (rot) that basically will drain everyone hp until you wipe. UNLESS you press your defensive early so your healer can outheal the damage.
This can be a mob with a long channel that cannot be stunned / interrupted, fire on the floor, magic / poison dots on players.
The real killer here is when one mob is channeling a big aoe pulse and another mob gives you a dot at the same time, this dmg IS usually unhealable ( atleast on higher keys ). And most healers can only dispell one debuff at a time.
There are many many tools to deal with this, healer can dispell one, give external (pain supp/cocoon in my case) or just try to pop all cds and out heal it, there are bigger raid cds such as amz, darkness, commanding shout, zephyr, barrier etc, that can keep you alive for one of these situations.
A good rule of thumb for using your own personal defensive this season would be, if you start taking damage - you are probably going to take more damage until you eventually die, press your defensive asap when you start taking damage, do not press it after you already dropped to 5% hp and start panicking. Your 20% dmg reduction wont help you if you have 2 hp and the next tick of damage deals 2000 dmg.
This will also show on the healers party frames so they will think, cool this guy is a baller and pressed his defensive so i can focus my healing onto the other two schmucks, i will also know that your defensive is on cd now for probably 1.5-3 minutes so if another damage event happens soon i should probably give you my cocoon/pain supp for that.
Obviously this doesnt matter in low keys cause your healer is probably a giga chad and outheals everything.
Gl in your keys, and make your healers proud!
Ps if this comes across as snarky or me trying to say i dont wanna have to heal even though i picked healer, that is not my intention. I love healing this season and i am having alot of fun playing this no weakaura version of the game. It forced me to read up on the other classes and become more proactive as a healer.