How about a new spell that would work like warlock Malefic grasp, but for HoTs.
=> Blossom : channeled spell. Heals for a small amount raid wide, and every second (reduced by haste) causes every hots on each player to heal for 50% of their periodical heal.
Or : casted, heals player that have HoT for 50% of their total heal.
It could be instant cast with a cd or with 1,5 sec cast.
You could pre-HoT player when there is incoming damage and have some "burst" heals.
Just throwing out ideas