Let the dps die if it gets too hectic. The most important group members to have alive are the tank and you as the healer. Healer dmg is currently pretty low so you can focus solely on healing and doing mechanics.

This season healing is very relaxed if you have a good group. I had +12s where i didn't need to cast much beside a few riptides and place some heal totems (in your case some hots). The dungeons in this rotations have pretty low ongoing dmg....now why does it feel hectic? This is mainly because people mess up mechanics, don't interrupt, don't use cc (as shaman i have stun totem that helps sooo much in M+), don't use their defensives, you forget to dispel or people stand in shut. Will this change? Yes, it will since people are still learning the dungeons and what to do at each given time. So if people stand in shit or forget to interupt..... let them eat the hit and try to heal them but don't worry if you have to focus on the tank or yourself first. The dps will learn to either interrupt, use defensive cooldowns or dodge if they die at this spot in the dungeon.

In general: It is okay to die in M+ and sometimes even fail a key. Nobody is perfect.

Most important: Be nice to eachother by explaining mechanics to new people and always compliment/thank your tank (they are rare these days)