I really don't see how anyone could find Rey boring in the ring. His matches are usually fun to watch, and they always have a pretty quick pace to them.
Now as far as the character goes, I might see why someone would think he could be boring. The whole underdog persona can become tiring after a while. Sure, we all like to see the underdog triumph every now and then, but when it's done so many times, it can become stale. But there's really no other direction WWE can go with Mysterio, especially when it comes to pushing him to World Champion status. Think about it, could we really believe or buy into Mysterio beating Jack Swagger, or The Undertaker in a one on one match up?
Now as far as the character goes, I might see why someone would think he could be boring. The whole underdog persona can become tiring after a while. Sure, we all like to see the underdog triumph every now and then, but when it's done so many times, it can become stale. But there's really no other direction WWE can go with Mysterio, especially when it comes to pushing him to World Champion status. Think about it, could we really believe or buy into Mysterio beating Jack Swagger, or The Undertaker in a one on one match up?