I don't think the looping tricks can seriously be used in high level play, especially when your opponent is putting proper pressure on you. I mean, you might be able to make an argument for a single arrow loop, but blitzing and raining are just too much set up and accomplish at most 4-8% damage MAXIMUM. There are much better things you could be doing with your time, especially considering every arrow you fire will weaken the next one coming out. After a few rains, arrows will do a piddly 2% damage per hit.
Short hopping, perfect shielding, and Shield dashing are useful for a hell of a lot of characters, but yeah...they are important for Pit as well, probably not more so then any other character who ahs a good one though.
I'll buy the usefulness of wing canceling and wing refresh...those are both pretty darn good situationally, especially the refresh for off the edge chasing, but wing Dashing...I dunno, it's really not that great of a tech really. It's okay, I suppose, but in the time that you've pressed Up+B and controlled not floating to the air and going backwards, you could have just dashed and pivotted, or simply walked to space yourself.