Well.. most of current armor gear is swapping primary stats as you change roles so it would be agi > Int. What i said about min-maxing is regarding secondary stats (crit, multistrike, vers, haste) and role specific bonuses (spirit and bonus armor).
So, if you decided to go mediocore one set of optimized armor is enough, with role specific accessories.
If my memory serves me right, druid secondary stats priority goes like this:
Balance: Mastery
Feral: Critical Strike
Guardian: Mastery
Restoration: Haste
So, by looking at this, best scenario is that, if youre going mediocore/semipro, you can easily use balance armor gear to tank as INT will switch to AGI and as secondary stat are the same, you wont even need to re-enchant/regem.
Ofc, all role specific bonuses (spirit/bonus armor) will say, but it will be grayed out since its useless to Bears/Booms.
That being said, as INT converts to AGI (and vice versa) same gear can be used for Feral and Resto too, but due to different main secondary stat you will perform decently and you would have to re-enchant/regem. So if youre casual/mediocore player you wont bother with different sets for different roles.
Off topic, but regarding what i said.. Of all healers Monks have the best advantage at gearing as their WW and MW specs will use multistrike, and taking in concern that MW monks are still spirit free they dont even need +spirit role stat on gear.