Discussions about bonus action healing, and in particular healing word, have been going around our community for a long time now. However, I'm not sure I've ever come across a satisfying solution. I was wondering if anyone had any further thoughts on this?

My problem

In my own campaign, I DM for five level 7 characters that, between them, have an almost unlimited number of ways to bonus action heal a downed character in a fight, to the point that there is no tension or excitement, or any real effect to the action economy, from having an ally literally fall to the ground unconscious.

We have a way of mercy monk with bonus action flurry of heals.

A druid whose favourite spell is healing word

and a celestial warlock with eight (!!) uses of healing light.

My players are experienced veterans who are smart about their actions in battle, they generally save their healing for out of combat between fights or only use it to revive 0 hp allies. This has made DMing any plot significant fight or big boss monster less fun to run as the party never feel threatened by a 30 damage hit if 1d4 of healing can bring them back in the fight next turn.

Now I want to make it clear that I don't want to kill my players. In fact I want them to win! but I want to challenge my players, and have them feel accomplished for winning. It kinda saps my enjoyment of the game knowing they have no doubt that they will survive against a powerful arc ending fight. I also have no problem with healing magic in general. I agree that healing may in fact be underpowered, except for this one particular strategy. I'd happily buff healing numbers if it would remove all bonus action sources of them.

Solutions I've tried

I've been DMing for a long time and always had issues with healing word and yo-yo tactics but never has this become more apparent than with this campaign.

Attacking downed PCs. I've seen this suggestion floated around but in my experience, or at least with this party, this doesn't work well. I've had smart enemies recognise the healing tactic and decide to start finishing off unconscious PCs, but unless they have a three attack multiattack to down, and double hit a PC in one turn (which also isn't fun for the player), then the enemy ends up wasting attacks on an unconscious PC which will get up with a bonus action anyways. Even when this does rarely work, it often leads to the enemies losing due to wasting time fully killing one PC only to die to the rest, and the dead player just feels like I'm punishing them in particular for their allies' healing abilities.

Focus healers. Smart enemies have also tried going for healers once they witness this tactic, but with three regular sources of bonus action healing this rarely works, and the enemies end up throwing themselves uselessly at the backline as the rest of the party kites and mops them up.

Penalities for going down. I used to run the rule of gaining one level of exhaustion when knocked to 0 in previous campaigns. However, exhaustion can get pretty punishing very fast so I scrapped that idea for this campaign. I've also used lingering injury tables and homebrew wound systems to give some lasting debuff. This also tended to cause death spirals and punished front lines more than others.

I've seen some ideas that suggest requiring the downed player to use an action to recover from being knocked down once they are conscious again, which helps with action economy issues but doesn't help the tension issue.

Maybe having failed death saves remain between instances of being knocked down? Recover on a short rest? I'm not sure.

Conclusion

One of my players, the Celestial warlock, kindly suggested he switches subclass to help reduce the problem somewhat. However, I'd rather not have players switch characters just to bring some tension back to the game. Nor do I think it will help much considering there are many other sources of bonus action healing.

I want to find a more permanent solution. Do you guys have any suggestions?