If it's Stone Vigil, the worst enemies in that dungeon are the Aevis and if you didn't notice they cannot be slept. They roam around the area and they will assist any enemies they are nearby. This includes if they are walking around and come across any enemies fighting, which is different than every regular enemy in the game.

Next time you get into a party try and let the party members know to take it slow and cautiously because these enemies will cause wipes quite easily.

Aside from that even if you are a healer it will be impossible for you to do your job if the rest of the players aren't doing theirs. This means the tank not having crappy gear and holding hate on enemies, DPS not pulling hate, and everyone staying out of AoEs.

Also check your weapon to see if maybe it is underleveled or damaged. The Magic Damage rating on CNJ weapons greatly affects heal potency and if your weapon actually breaks your heals won't even break the double digits.