My two issues with showdown are the sliders/advertised difficulty level and that you can't use your own DD team. If they advertise a showdown level at veteran or all-star, then it should play at veteran or all-star...Otherwise, just say it's at Hall of Fame difficulty and they would get much less heat because would be setting the proper expectations.
Second, I wish you could use your DD team. Right now, if you want to play offline, the only two modes where you use the team you work hard to build are conquest and play vs CPU. This seems like a wasted opportunity by SDS because they want to encourage people to spend money on micro-transactions and if people (like me) are having trouble on showdowns, then maybe they will spend money for better players.