Possible card for UG06, this is the kind of vanilla I'd want at uncommon.

Well, Woolly Thoctar was awesome in Limited, but isn't this a bit too strong for Monogreen? Maybe make it a Leatherback Baloth instead? Also not sure if encouraging Monodecks is a good idea. It can work in Green though.

I don't think that this one card encourages monocolored decks too much, maybe in constructed but unless you open up two of these in limited I don't know how much I'd want to build mono green for one of these guys. If the stats are the problem I would rather make it a 5/3 than a 4/5, a 4/5 just doesn't feel as aggressive and is probably better in most situations that a 5/4.

Well, it either encourages a monocoloured deck or makes this card a slightly bad filler. The stats should probably be 5/3 or 4/5, since 5/4 for the same cost as Woolly Thoctar but less restrictive is just too much. Woolly was awesome play in Alara Limited if you got it out in turn 3, just so much pressure and needs to be handled as soon as possible. Same with this if it stays that way, I would honestly try to force mono Green or majorly Green if I had that card. Attacking for 5 in turn 4 is super strong.