I've been through Pixie Hollow twice. Once was first thing in the morning (about 1/2 hour after opening), and second was on a slow, kind of cold day...right before they closed. Each time the wait was about a half hour. Each time there was Tinkerbell and only 1 other fairy. I'll be honest....totally not worth the wait for me...or even my daughter. She loves tinkerbell, but not a whole lot of bang for our buck.
For me, I guess I'm comparing it to our meeting of the princesses....we had 4 princesses, and they were much more interactive with the kids...and just about the same wait.
The good part about Pixie Hollow is that you can look and see exactly how long the line is. If it's into the back-and-forth section, you've got anywhere between 20-40 minutes, depending on how far back into it you are. If it's almost back to where the sign/greeter are, you're talking anywhere between 45-60 minutes.