Honestly, I think it's fine as-is, given that other classes get better for free.
This sort of statement is really not true. To get access to "better" (e.g. spells that let you escape) requires an investment into enough caster levels (13 to 14) that you have to be a caster; or having scrolls and the UMD to use them as a Rogue/Bard/Assassin. There's always an opportunity cost.
Hell, let's analyse Monks, since they get both a "for free" not really free ability like this, and are a class that could easily take Shrouded Dance, since they have in Class Perform and Hide.
PotM Monks get empty body at level 18, which lets them cast Ethereal Jaunt once per day. This isn't really "for free" because it commits you to being a high level Monk to get it; you can't, for example, be a Monk/Assassin and get this.
On the other hand, Shrouded Dance as currently written, any level 9 Rogue, Monk or Bard can get this at the cost of -- effectively -- 1 feat and 5 ranks in Perform (since the investment in Hide is taken as given). This is a extremely low opportunity cost that closes very few doors. You can be a pure Rogue, Bard or Monk and do this; or you can still easily play your Rogue/Ranger multiclass or your Rogue/Assassin or Monk/Assassin or Bard/whatever and do this.
So you see: on the one hand, the Monk can choose to go for Empty Body -- but in that case he can't take a Prestige Class -- or he can go for Shrouded Dance, and do whatever the hell he wants.
If I'm a Wizard or Cleric, then that comes with consequences of being a Wizard or Cleric or that level. Nothing is really "free".
One should beware of introducing choices in the game that are too easy to make. The choice to take Shrouded Dance as written is an extremely easy choice to make for the return it gives. Even at Perform 10, I believe it's an excellent deal.