There's a Balance Druid/Warlock combo that I've run into a few times in 2v2, they do really well. Druid's armory is here -
The World of Warcraft Armory but it appears he/she has switched teams since hitting 2k as Druid/Warlock. if I recall correctly, they ended last season around 2200ish.
It's definitely doable, but a different playstyle. Resto Druid/Warlock is probably easier, but the spec is absolutely viable if you're willing to work at it.