dave2008
Legend
Another consideration might be: How likely do you think it is that your players will trade an Attack or Spell action to end the ongoing damage?
I know that when granting a save with a standard action Heal check in D&D 4e was only used in truly desperate situations. And I know that my players at that time were never happy trading an attack to do it. Your players may be different, of course.
If the ongoing damage is also tied to disadvantage and loss of actions, as proposed, highly likely. If it is just ongoing damage it would depend.