There's currently a strange bug that could be the source of your troubles: if you or a group member have a pet out and the pet takes damage, your healing Companion will stop healing players! Unsummoning the pet will make your Companion behave as intended. I'll be sure to put this on the Known Issues with the next update.
Please post here if you find that your healing Companion Character isn't doing their job and it isn't related to your pet. When posting, please provide as many details as you can and we'll be sure to investigate.
I have actualy run into this but i think i found a work around, if you turn off the cc which is usualy carbonize stream they continue healing, its as if they are trying to cc but with the new rule set upon them where they cant cc npcs under x health they will attempt to but the rules stops them, they get a headache and pass out.