I'll be the first to admit that the plot really does die off after the Jedi Masters are killed and Kreia reveals herself, but it is by no means a letdown.
And Bastila only shows up if you said Revan was a male. She shows up after you leave the room with Carth and talks to him a bit. She says something like "I only wish I knew why he did it."
And it's obvious from the get-go that Mandalore is Canderous. He says "Clan Ordo still survives," and Kreia asks him to "find out why he left you there on your own," obviously referring to Revan.