Perfectly valid use of Tenacity.
I'm not usualy running savage on tank, so I tend to meld Tenacity too, it softens the blow of being undergeared.
As a result I was able to very comfortably clear Ruby EX as an i461 GNB.
(It's quite annoying that so many PF specify 470 minimum, when I can probably do that fight better than most others)
I may take my GNB forward more as a main now though, so if I'm up to gear I'll probably want more damage over defence.