A while back we did have a thread about a lvl 70 Boomkin running as tank is the nice big instances. Sounded different but very hard to pull off.. Well I have had some thoughts on this and an interesting experiance.
Was off to Zul'Farrack the other day, PuG as usual, and ended up in a group with a Shadow priest (who i had been with before) 2 hunters and a fire mage. All in all not a lot of tanking power. I play as balance spec but with the only one near a tanking ability I went bravely froward as a bear and tried to hold aggro... That went down like a lead balloon. I admit I haven't got any decent tanking gear at all so it wasn't totally surprising. So instead i though sod it, moonkin has 400% armor, why not try it.
Have to say, It worked really well! The mage loved me (+5% crit!) and with the priest on heal we managed to do most of ZF fine. Then we lost one of our hunters and another druid came in, guess what balance as well! So we finish of the rest of the dungeon, (we had only done the basilisk boss with just me) including garzilla with two moonkin tanks. DPS was great so things went down fast and with us two holding aggro through sheer DPS we kept the party alive just fine!
So it can be done (at least at lower lvls) even with a PuG. Well as long as they are careful. Just not something I would like to do all the time, a nice pally or warrior or feral druid is gonna do a lot better!