Well, first of all, Daring Do is obviously a recolor of Rainbow Dash with nothing changed to her model. They also reuse cutie marks all the time, and background ponies. And some of the backgrounds are kinda half-assed, too.
You're kidding, right? The entire reason Daring Do was a recolor was so Rainbow Dash would find her more relatable when she read the book. I think the animators are excellent. They could have just as easily have gone with Johnny Test style animation.