Lets see. 30%, 10k down, another "10k" hit coming in while everything is active...
Heart: .85 * .85 * .7 = 40,460.
10k with: .85 * .85 * .7 = 5,057
10k w/0: .85 * .7 = 5,950
HP with: 24,483
HP w/o: 25,376
900 heal: ~13,500
Crit@50% modifier: 20,250
BW: .9 * .9 * .7 = 45,360 - 6000 (BW shield) = 39,360
10k with: .9 * .9 * .7 = 5,670
10k w/o: .9 * .7 = 6,300
HP with: 24,970
HP w/o: 25,600
1600 healing potency: ~24,000 (We're 10k under, so there is no overhealing)
GNB Final Total
With: 37,983
W/O: 38,876
Critwith: 44,733
Critwo: 45,626
BruShell+: 6,000
CB Shell+: 9,000
Warrior Final Total
With: 48,970
W/o: 49,600
===================
Show your math. I think it's off. Granted it's possible mine may be as well, but that's why its posted - so it can be critiqued.
I'm also not going to use specific GCD usage, because that varies depending on when the ability is used. Gunbreaker during cartridge combo or Warrior during IR compared to one that isn't doesn't actually have anything to do with the strength of the individual cooldown.
I'm also not going to include healer intervention. Seems irrelevant if you ask me, as an outside factor. it would be like saying "But if you have really good DPS players, then the boss died a minute earlier and this tank buster doesn't matter."
Edit: Forgot to add Brutal shell. Also forgot any sort of crit table for Warrior, but frankly I don't think it needs it. Adding brutal shell prior was just a concession that it probably would be active going into a tankbuster, but that still depends on where the Gunbreaker is in the rotation compared to when the tankbuster is incoming.
So in short, as long as the Gunbreaker crits absolutely everything, it is, in fact, better than a Warrior who crit nothing. Though if we were being fair, giving warrior both one Storm's Path and two Nascent criticals, well.
I don't think we need to do that.