strenght flask is actually best for prot warr (larger shield barrier), as talents go, indomitably means u take more dmg overall, and cut deeply into your rage generation, which means u will have wholes in block uptime but have 20 % more hp. But 20 % hp wont help survive unblocked hits on aggramar
so for your warrior i would say he is doing stuff right, its just a very hard class for the player compared to all other tanks, prot warrior are the least used tanks in this expansion for a reason, because of the hardcore nerfs early in this expansion.. last time i tanked in raid (normaly im dps) i helped out in nighthold mythic, and jesus this shit was so fucking hard to do as warrior tank. I switched to a 20 ilvl lower blood dk, and stuff that woulld kill my well geared warrior, that used cds and external and stuff in a complex rotation via voicecom was suddenly piss easy faceroll.
As 950 warrior you get oneshotted at m12 first boss in maw of souls with boss-trait without cds, and after 3 casts from the boss, u are out of cds, so u need externals (or the new leg legendarie for extra spellreflect charge). all other tanking classes laugh at this stuff.