I agree with this, and I just wanted to bring up a specific example of where I absolutely love healing amp.
Depending on how you run the hound, your intimitank may break from the Xyzzy when all the dogs are charmed, so as to be able to engage any trash that wanders into the center (I know some groups prefer to keep intimidating the whole time).
Typically, if you have been blocking (and not strafing) there is a high probability that you will have bees by the time your intimidating stint is done (and the clerics will often be pre-occupied with the dogs at this point, leaving you to die).
A tank that has >200% healing amp will be able to keep themself alive by chugging csw pots.. This is the way to my knowledge of self-sufficiently surviving bees (as you cannot cast while you have bees), and its kind of neat to stay alive on your own accord when the clerics expect you to die. I would guess that you could make do with a lower healing amp % if you were also wearing bramble-casters.
This is just one very specific example,but healing amp has many places where it shines in the game. That said, most people will never know how useful it can be (because I find most people don't appreciate it until they have put significant effort into getting their healing % to a high enough level). Its kind of like AC: you have to get to a critical point.(i.e. you don't really appreciate the difference between ~20 and 40AC at end game, but you sure appreciate the difference between 40 and 60)