I just finished solo leveling my feral tank druid just a few days ago, and the aoe is really great. On top of that you have quite a bunch of defensive cooldowns in bearform.

This could really work well to 3 box as swipe has no facing requirement. Once you get beserk & trash it gets even better. Spam mangle every 3 minutes and see the mobs just drop like flies.

The main strength of 3x bears is that swipe has no facing requirements, you have 3x aoe taunt if some toon is in trouble, you have 3 cooldowns and decent self healing.

Definitely worth a shot if you ask me.

Tip: there are some very good youtube videos and forum posts about where to aoe grind (I don't have links but google should net you quite some info). Worth it to research your leveling plan more or less beforehand, i.e. know the spots you will grind and from what level to what level. So you also know where to quest.