It does disappoint me that Wendy isn't bringing her personality to the dance floor. I figured that'd be her saving grace (maybe), if she couldn't dance, and if she was fun, people might want to keep her around just for that factor. But the last two weeks, she didn't even seem like she was enjoying herself. I think this was just an exposure move to make her more well known, and she doesn't want to put the work in but doesn't want to look bad. At least that's how I view it. I'm sure the producers were expecting the Wendy from her talk show to show up on the dance floor, and that hasn't happened.
ETA: I'm surprised Mark/Chelsea have gone so early every week so far. They just seem like a couple I figured the producers would want to save towards the end. Mark made whatever point he was aiming for with their jive, so I figure they'd tone it down for the cha cha.