This is absolutely 100% WRONG.
If you kept the Shire gear all the way to 70, you'd have 2286 Defense while doing so. Roughly 29,991 hp from gear from 1463 Vit.
Compared to a tank that took the HQ quest gear (285) literally given to you while leveling. Or equipped any gear that was given to you automatically when you completed a SB dungeon. Or bought the NQ gear sold by vendors in Kugane.
They'd have 3828 Defense. 31,918 HP on gear from 1557 Vit. They have 67.45% more defense than the person in 270 gear. While that doesn't mean you'll take 67% more damage than the better geared tank, that does mean you'll take a ton more damage from every single hit every trash mob does to you. All those hits add up to a quickly dying tank. All the Vit in the world doesn't mean anything when mobs are taking chunks out of your HP pool instead of nibbles.
Just for reference: The Defense gain from 310 to 380 is LESS than the defense gain from 270-285. It's an 18% jump in defense from 310 to 380.
So no. Do your healers a favor and upgrade your darn gear so you don't melt during dungeon trash pulls.
To OP. Is it wrong to be in CA at 272. In my opinion yes it is, but that's just my opinion. Just realize you're making your healers life really hard to keep you alive if you do decent sized pulls.

Originally Posted by
Bourne_Endeavor
Just for fun. I did some basic, dreadful, MATH. A DRG rocking the full Gazelleskin level 68 set will have 2680 defense. Mr. Shire tank will have 2286.
Let that sink in for a moment.
Edited: for better, more accurate numbers