It's fast, it's tanky, it can blind with the 'bloody pecker' edge I think, the regen is awesome, it's FAST. Hell I've seen people PK with JUST the hummingbird.
Damroll is not how you want to rank how deadly forms are in PK. There's more to it than that. Some of it is playstyle too. Some players like util forms MORE than offensive forms for PK.
Sorry I wish I had more to tell you but that's really about all I can think of. Keep going for your final forms without using hummingbird if you feel comfortable doing it. Good luck! :)