Not sure who or how such a list could be compiled, because everyone would have a different take on this. You may hear a song and can't figure out the bpm or underlying beat for a certain song, but I could figure it out in a second -- and vice versa. I guess what I am saying is there would be no universal list of "songs that are hard to determine a dance." Songs on that kind of list probably aren't suitable for ballroom?
Also, I'm with you Polished on the starting points for rumba or cha-cha. We are working on a cha-cha routine right now for a local fund-raiser competition and it's a difficult routine, but more so because I can't trigger the proper start each time and, as you said, if you don't have it right at the get-go, the cha-cha is unforgiving -- it's hard to regroup and get back on the timing without looking choppy and, well, lost.