Yeah, it's been interesting. It started out as a "my kung fu is stronger than tae kwon do" peen competition, primarily organized by the Gracies IIRC so they could prove that BJJ had the largest peen. Which it did, for a long time, but with the introduction of rules, and a LOT of water under the bridge, it's evolved into its own thing. Just bringing any one discipline to the mat is a sure way to lose to a stoppage. Fighters now to have to be skilled in stand-up, ground, and be very physically fit* to have any chance of getting into the UFC, and it wouldn't surprise me if the b-tier leagues are becoming nearly equally competitive.
* Roy Nelson has me confused here as well.