I had a friend who was already working on Hell, and when I told him I was using RoF he laughed. "The damage on that is awful!", he said. He doesn't pay attention to the tooltips. I told him that with the ramp up rune and Cold Blooded passive the damage is comparable to Archon beam (I didn't have Archon yet at that time, but I knew Arch beam was 300%). He replies "No freaking way. I'll test it right now." He then tells me that maxed out RoF seemed to do about half of what Arch beam was doing.
Later I get Archon, and test for myself. Sure enough, the 300% arch beam >>> maxed out RoF. But why? Do the tooltips lie? Is something bugged?
I then start watching the numbers that pop up off the mobs and I nuke them with RoF. They look low. I notice that I can kill things about as fast with free to cast signature spells as I can with RoF, even though the RoF tooltip *says* it does much higher damage. I also have yet to see any video of Inferno wizard play that involves RoF, even on single target fights.
So yeah...what's up with RoF?