Is something they did to combat. In the challenge maps you now are being forced to use the variation bonus if you want to have a better chance at 3 medals. Variation focusing on gadgets. In AC I managed to get 3 medals and some very decent scores without a major bonus to variation. I never liked using gadgets in combat; they always broke my combo. Some people are good at them and some are not.
I don't do too bad at all in the story mode, but the challenge maps are a different story. In AC, the variation bonus was an option. In AO it's a requirement. This was a real let down for me.
Other than that, I like the game a lot. But, if you're not good at the variation bonus, 3 medals will be very tough to get.