The thing about jungling in TT is it requires a lot of communication between the lanes and the jungler. It is a lot harder to be successful at jungling in normal TT than in ranked or doing normals with a team of three because the jungler has to rely on his laners almost more than the laners need to rely on jungle. By this I mean if someone goes Mia the laners NEED to let jungler know ASAP so that he can determine if it is safe to continue jungling, or if a play can be made if the other lanes collapse into the jungle. Having reaction time to make sure your jungler stays safe is probably the most important factor in jungling effectively. That being said, the benefits of jungling successfully are amazing. By 10 minutes my team is usually 1-2 levels up on at least 2 members of the opposing team. The extra source of gold income from having jungle camps constantly down allows for stronger teamfights as there isn't a low farm champion that is "only there for cc". Ganking presence is also something to factor in because as a jungler you can easily snowball the 1v1 lane if either of you has good cc. Picking a strong 1v2 champ is also important if the enemy team doesn't jungle. Again, all of this is dependent on GOOD COMMUNICATION between the lane players and the jungler. Having a jungler also makes it a lot easier to catch your opponents off guard for an easy alter steal or vilemaw rush.
I prefer quick junglers with extremely strong initiation such as amumu, jax, riven, shen, hecarim, dr mundo and shyvana. Always build your team with the teamfights in mind so that you don't "lose in champ select" which can happen pretty easily in TT.
In conclusion, jungling good, duo lanes bad.