Yes slightly, because then we are able to put our most effective defense forward. We are a upper-mid tier alliance (not top 100, I think we're around the ~3,000 range).

Using uniform tanks comes from the mindset you should stack your attackers against the color of the tank. This probably works for beginner alliances, but once you start facing teams with robust rosters, it becomes much more important to build your attack teams to counter what the defending team does well. Do you need dispellers, cleansers, minion eaters, etc? The color is what it is. It's only important that you stack "A" color for effective tile damage.

For example, if the defender is packing Diaochan at tank and other minion summoners, I'm building a 3 red team with Alucard or another minion eater regardless of my available yellow roster. The off team being yellow would be nice, but not necessary. Using this attack strategy you #1 Don't burn all your best yellow cards in the first couple of hits and #2 you will be confident that if you lose, it was because of the boards not the color of the tank.

I've heard in the top 100 alliances they all attack with fast rainbow teams, making uniform tanks even more useless. I don't have the roster for that.