So here's the idea to fix whack-a-mole:
If you're 1 hp or above, cure spells are instant. If hp 0 or below, cure spells take 1d3 minutes to work before the target is healed.
No more whack-a-mole?
What do folks think?
While I personally have no issue with "whack-a-mole" this solution creates a problem in my eyes.
A character falls in combat, perhaps suddenly due to a crit. The cleric rushes over to heal them, you roll that t takes 3 minutes to heal them. 30 rounds of combat. Within 6 rounds the character is either dead (and thus the cure spell is wasted) or they are stabilized.
Meanwhile, 2 players are out of the fight.
So, the healer will now never attempt to save an ally who falls in battle. They will wait til after the fight because it is impossible to save them before the death saves will run out. This means a player who falls is left sitting the rest of the fight out, until they either know if their character died from their wounds or will survive and the party can do nothing to save them.
Unless you still allow medicine checks to stabilize, and then I have to wonder if the healer feat can still heal while their at zero, and that makes a non-magical heal more powerful than a magical one.
If your table wants the game to be that deadly, then go for it, but personally I think it is a more tense and tactical battle where the healers have to see if they can reach a fallen ally and give them enough healing to survive long enough to retreat or get out of the line of fire.