What's good about them? Well, if you use it with another piece of Champion's you get the 2 piece set bonus (Robes aren't required for this, though). Crit chance is nice. The best thing about them is that they are black in a world of pink and purple. Besides that they are very...meh. More of a status-symbol than anything. With the amount of time you spend getting these you could probably walk away with Arcanist Robes or Flowing Ritual Robes several times over.
Are you insane? Even if the other stats were worse than your normal green chest piece that 1% chance to crit makes the robe worth it.
and 100 int= 1% chance to crit.
So that that robes 1% equals 100 int.
That makes it a very fricking sweet robe which ever way you look.