Gotta agree, I built a horde of scrappers to see what was most fun for me and the Katana/SR is by far the most enjoyable and solo's best (claws/Dark Melee with SR being the others. I gave up on Dark and Regen secondary because the endurance drain of one and the christmas tree effects of the other just rubbed me wrong)
Upon reaching 8th and getting DA I was sold. I have no other non-tank toon that can dive into a horde of a dozen even cons with a couple lts and come out on top. With the dark melee guys I run out of end and get hit too much, but with the Katana my endurance doesn't suffer as much, I can effect a much wider cone than Maul, and DA stacks on my FF and CJ to make me nigh unwhackable as long as I can keep the enemy close.
Such a great power, and although you mention it's benefits are better noticed with non-SR secondaries, I gotta mention that WITH SR you're just that much more untouchable, plus you don't need hasten so much as a DA every 3rd strike is a major boon.
Super sweet power. Katana may not be the heaviest hitter, but you get more time to use it!