Horwath
Legend
yeah, healing surges, or at least maxed HD is better option for this idea.So like, there's a decent concept here, but it has two problems:
1) Hit Dice (which is what I presume you mean by Healing Surges) don't scale in value, they scale in total number. Whereas incoming damage scales in value. Thus the HD would make less and less and less of impact as levels went up, being almost entirely meaningless by the mid-levels. So you'd probably want to let people spend more than 1 HD at various levels - perhaps the same levels a Fighter gets extra attacks or a cantrip increases in damage?
or you can spend HD every round you still have them.
That is why I suggested that ALL healing is FIXED amount.2) You could potentially get into some pretty upsetting/frustrating situations where a group just didn't have the HPR to save a PC, or almost did, but only if they rolled really well. At a certain point, people are also going to work out that trying to save people who've taken too much damage is "throwing good money after bad", because Revivify is a 3rd level spell, and so long as you win the fight, it's a lot better to just cast Revivify than pumping a ton of spell levels into a dude to try and get him back up (which would be wasting Actions or Bonus Actions, turn after turn).