The underlying problem is (at least with most end game content) you typically go down from one-shots as opposed to repeated lesser hits. This means that stacking toughness, vitality, healing, and regeneration are fairly pointless for some classes, since you're going to be one shotted regardless of stat setup.
This. The way the game is balanced, healing isn't intended to be the form of support. In fact, I get the feeling you're not really intended to go the healing route at all. Any gear/traits you spend on pumping up your healing power would be much better spent on raising your damage instead. The return you get for investing in high healing power is so poor that you end up with pretty weak heals anyways, at the cost of making battles drag out longer, creating more room for your group to make mistakes and die.
With the way GW2 is balanced, your best bet for support is to go with condition removal and boons that aren't regeneration or protection, in PvE at least. Don't get me wrong, prot and regen are nice to have, but when you're in situations where an enemy will spike you down in 3 seconds or less, the ~450 health you get from regeneration isn't going to do much, and protection probably won't make a difference anyways. It'd be much more beneficial to the group if you keep dealing consistently high damage while giving aegis, vigor, swiftness, stability, reflects, and blinds.
There's also the option of going support via c/c. A mace/mace + hammer berserker warrior taking Furious and Burst Mastery would be able to spit out c/c, which could be great for stripping defiant stacks on a dungeon boss to interrupt a big attack. It wouldn't do as much damage as an axe/mace + greatsword warrior, but it wouldn't be poor damage either.
In short, don't focus on healing. It's not what's meant to be played in GW2. Focus on other forms of support.