As above, healing rain > chain heal > other stuff. In raids anyway.
Deluge also isn’t just riptide, but targets within healing rain. So, if you decide to take it in m+ healing rain first then a boosted chain heal with the new tide bringer, since more targets in m+ isnt needed.
Chain heal focused builds can work fine in the m+ scene so its up to you if you want to roll that way over undulation.