I just tested a heavy borean armor kit on chest - even without kings (ie, at all times) it's still better than 275 life. +10 all stats is still interesting in comparison - but even still, the 'feral' spec doesn't necessarily hang from the stamina bonus there. How about cat form? No %stamina bonus there.
It's tough - I'm still inclined to treat feral druids as tanks by default if there's no autodetection (as imba does, whatever their algorithm is).
Thankfully at least there's some more respectable idols coming in with 3.10 - haven't yet seen a great tanking one, but hopefully it's on its way in!