Thanks for the answer!

What was strange about that is that ALL of the Healer's gear was synced (as I said most of his gear was NQ and ilvl 25 - 29, one piece was 22 or so) and he still had way more HP than Healers beyond level 50 actually have synced to 20.

That the tanks below level 29 sometimes have less HP is normal, I know that, but that the Healer had more was kind of strange because he didn't have non-synced gear. xD

There also seems to be an inconsistency as equally geared players sometimes have more, sometimes much less HP in synced content.