Thank you Sarova. I completed the entire bounty hunter class story about five years ago then stopped playing until recently. I have no class missions in my mission log, except for the Rishi one I just picked up. Before I started Revan I did actually read the warning about completing prior content. Therefore, I first checked my mission log and legacy achievements to verify that all three chapters of the BH story arc have been completed.
Last night I submitted an in-game bug report showing the error message for the Rishi mission and confirming that a) I have completed the entire BH story arc and b) I have no class missions in my mission log. We'll see how it turns out...