I've actually been pleasantly surprised with Mandy.
At first, she was just the Tough Enough girl who was supposed to be eliminated early on before The Miz used his lifeline to save her since 'she was hot'. She ended up on Total Divas and really wasn't doing much of anything in NXT till they brought her up with Sonya to add some bodies to the Royal Rumble. I thought they would both get swallowed up, but Sonya is a natural and to her credit, Mandy actually carries herself well. She doesn't come off as a typical diva, she actually gets stuck in and executes some pretty believable throws.
I think she was really smart to pitch the Otis idea and give the WWE something they can sink their teeth into. I'm not sure what the end goal is, but it's been a fun ride and it's elevated everyone that's been involved. Even Dolph is doing better after being Corbin's lackey.
Essentially her appeal is that she's a bikini model who understands show business and can actually work a passable match which is more than you can say for a lot of people with her experience. Her social media work is fantastic as well, I believe she held the record for most engagements around Wrestlemania time. That extra curricular stuff goes a long way, look at how Becky used it to get her run on top.