I think attendance at all regionals is hurt by one main factor: Economics.
College hockey is a niche sport. How many fans from Grand Forks or Princeton will pack up and go see a regional in Madison, WI, then turn around two weeks later and head to Denver? Most will hope their team makes the Frozen Four and make a trip. This isn't NCAA basketball where you stick a regional in nowhere-land and maybe people will come to see Kansas, Duke, or North Carolina...OF COURSE people will go see those teams play. The fan base is much bigger.
Travel costs aside, I think the NCAA needs to get back to schools playing host to other schools. You're #1, you get to host #16. You're #8, you get to host #9. Your team barely qualified for the tournament as #15, you don't get to host a regional, you go on the road.
Like I said, I know the travel costs is a big factor for the regionals but college hockey looks just sad playing in 10,000 or 12,000 seat venues and there are 1,000 fans in attendance.