I personally have a DB/WP Scrapper....granted, he's only lv 10 though, I think. I started him along with a WP/DB Tank when they first hit, just to try them both out. Running on a team with 3 others of the same Powerset/AT made ki...er...arresting quick and Leveling at a decent pace.
I have a Katana/Regen whom I like a lot, he's only 20 though.
I'd say, of the short experience I have with the Powersets....and this is really a personal choice...not really the "right" choice, if there really is one....DB is good with WP for Scrappers. Basis: With the damage combos from DB, and all the stuff WP has to offer, you'll defeat the enemy without needing a heal. Rather, you would recover faster, so you wouldn't really have to worry about your HP unless you get into the red, period. Just don't go into a group of +2's or +3's on half health and think "I'm invincible". Then again, with /Regen, some similar perspective of not doing that is appropriate.