I've been hearing proactive and reactive used with the word mitigation since 2007... nobody is reinventing anything. Not to sound like an old man but I've been around the block and I've played several games and I always play tanks and I always talk about them. These things are often brought up in discussions of mitigations and how healing tools work to make mitigations stronger. And I thought I made it clear my mind cannot be changed, I know certain healing types are mitigation and can use words beyond "No, I don't think it is" to back it up.You are being pedantic as he said, the math always shows the same results. Percentages are some of the easiest things to use in math and all mitigation is is a percentage applied to a fluctuating flat value. It's just numbers, which is what makes it easy to resolve. That alone is enough for me to respectfully disregard your notion as I've really nothing to prove, I'm a good tank and my group agrees. I could stand to improve my DPS a bit, but it's never been a question if I know how to use defensive cooldowns and appropriate my abilities to situations.
It's like this. The sky is blue, but someone might try and say the sky is not technically blue because wavelengths of all colors come through, the particles in the air that cause Rayleigh Scattering are blue. But it doesn't really matter what the source of what I'm seeing is, the sky is still blue.
The only real reason to say healing is not mitigation is if you forget you take more than 1 hit and that all of the damage is not instant. The other factor in your eHP is the duration. How much eHP has to be burned through over a period of 10 seconds? That's very different from how much eHP has to be struck in a single hit. The barrier type mitigations only ever matter over healing in a single hit, meaning tank busters, which every tank can deal with so the question is how well can the tank deal with it, and if they take spike damage but immediately cap themselves off again, which is the tankier tank? The one that ends with more HP is unquestionably more defensively capable. If mitigation was exclusive to shields and percentages then Arm's Length wouldn't be considered mitigation either.
And for what it's worth, the word "mitigate" literally means "to make less severe or painful or to lessen the gravity/effect of" and heals in this context perfectly fit that definition. Healing of the aforementioned type does in fact lessen the severity, pain, and gravity of the damage taken. I cannot be more clear about this. Nobody is reinventing everything. That is the literal definition.