I'm emphasizing the importance of versatility. Being able to both restore hps, and mitigate damage - in different ways and different proportions - in response to the challenges your party faces is versatility. Doing only one or the other or having them available in only a fixed ratio is lacking versatility.
Would healing be a good pre-combat buff? Maybe; if party member hp < 100%. But mitigation, via temp HP, would ALWAYS be a good pre-combat buff. It would even help in case someone fell in a pit.
Which would be better? Healing 7 damage or preventing 7 damage? Tie, right? All things being equal, that's a tie.
Which is better? Healing someone from zero to 10 HP, or causing an attack to miss and not drop an ally? Depends on turn order, doesn't it? If the ally isn't going to lose an action due to unconsciousness, it's equal. But if the ally would miss a turn, the forced error ability would be better.
What would be better? Healing some damage after a failed save, or causing a successful save? Gosh, depends on the amount doesn't it? Might not take any damage at all if you save. But full damage from a failed save and then some healing? Eh, not as appealing as making that save.
Here's another. What's better? Making that save vs charm/compulsion or healing ... Uh... Uh-oh, charm and compulsion don't do damage. So mitigation wins that outright.
See, as long as all you consider is numbers up and numbers down, healing will seem to be the best option. And it IS A GREAT option. But mitigation is fundamentally the SAME level of awesome. You just use it differently.
So if your critique is that mitigation worse than healing because it doesn't work the same way, you're essentially complaining that your saw won't drill holes.