HP in level synced content

Hello!

I really don't get this ... how exactly does level sync in dungeons work for HP?
Yesterday I did a Low Level Roulette as DRG, I was level 43 synced to 20 or so (I got into Copperbell Mines). I had 489 HP. My gear was crafted with two GC pieces.
The Gladiator was level 20, non-synced, his gear wasn't so great but ok. He had 490 HP. Everything as usual.
The WHM though was level 31, of course also synced to 20, had normal quality gear from level 22 to 29 or so. He had 491 HP - one more than the Tank. As far as I know he didn't have any food buffs or so.
I even have a screenshot of another Copperbell Mines run and the WHM was synced from about ilvl 90 - 93 and had only 435 HP. When I was WHM synced from about Level 40 I also had 435 HP.
Why is it like that?

Also, when I get into Haukke Manor as White Mage I'm always the only one with under 1000 HP. Also the same when I'm Bard.
Equally or worse geared WHMs and BRDs (let's for example say about ilvl 80 – 90) always have more than 1000 HP in that dungeon. Why??? Does everyone besides me put all their attribute points for non-tanking classes in VIT? xD

How are Vitality / HP scaled in synced content?

I thought all attributes get scaled to normal quality gear for the max level of that dungeon.
I get that someone with green gear from that dungeon can have better attributes. But when both are synced it's kinda weird. O_o

Sorry for the long text, don't really know how to explain it. xD

(assuming you get synced to lv20) Non-sync players often have gears not up to their current level, like having a lv17 gear for a lv20 class so those gears will not be synced as it didn't go beyond the dungeon lv cap, an endgame/higher level player will most likely have all theirs synced to 20 so they get the maximum VIT and other stats in each gear compare to non-synced and will often have more HP than the Tank.

Also, you don't get to use the gemstone accessories until you're lv28-29 so a synced non-tank will seem to have more HP than the tank because the tank themselves lost a significant portion of HP because most if not all accessories before the Sphene set (it gives VIT bonus) doesn't have VIT at all.

All these are based on my past experience, hopefully it clarifies anyway.

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.