I think it's more of a "playstyle and team" question. If you deem yourself capable of good CD usage then a 2min 30% heal + 30%maxHP for 20 seconds is worth one less quality item IF your healers can make use of it.
I guess personally I would use the T14-2P. As I am raiding in a mediocre skilled raid there are several situations per bossfight where 30% heal + more max HP for 20 seconds are a nice lift for the healers.
Also think of an "Oh Shit" Situation as a tank.
Normally all healers go crazy on healing you that time. You will probably find yourself in that 0-100% situation. One second you are at 5% health (where you activate "Last stand"), the next second you are at 100% because every healer got their hands on you.
Having 30% more max HP as a buffer has 2 merits: 1. You take less overheal in that shockmoment and 2. You can take a few more hits before your healthpercentage has dropped to critical again.
my 2 cents
PS.: The benefit of last stand doesn't change, so you get the effect of it regardless of T14-2P or not. It's just nice to have it every 2 minutes instead of 3
Situation changed abit tonight after clearing Sha and tonight's farm bosses. Im 485illvl atm, got 496 T14 gloves (with legs is 2/5 set bonus) and now im considering to replace same items as in 1st post though Ill get 4/5 set.