Rampage's main weakness has been that his skillset has been too basic. His offense is basically his boxing skills and power. His defense is very strong, but its always the question of whether he will be able to put together enough offense to hurt his opponent. I don't think Silva has close to the same kind of movement as Machida or Evans, and I see Rampage being strong enough in the clinch to keep Silva from taking him down and being able to batter him on the feet.
I also agree with some of the previous posters saying Vera is a worse match up for Rampage then Silva. It was just really surprising that Silva took him down so easily. Couture couldn't really take him down, and I would think Couture would have far superior takedowns. Vera was a very high level Greco-Roman wrestler at one time. I think his mind might just not be in the game anymore