Just my two cents I didn't make a katana/wp before but I have a katana/SR and DB/wp scrappers.
First katana part;
Divine Avalanche is not part of your damage chain its part of your survival chain so remove damage SO's from it and put defense ones and put a recharge one if possible. Gambler's cut in SO only build is also not for damage remove three damage SO and put defense debuff ones ır put sting of wasp instead if you want to keep damage SO's. You get build up too late you should get it as soon as possible.
Second part WP; I am not at a high point in WP so its all just suggestions IMO. With double stacking DA (you should be able to even if you don't put recharge in it) It will be enough to keep your lethal and melee defences at softcap. I am not sure 6 slotting high pain tolerance but I really can't find a good place to put those slots in anywhere else. If you plan to use strength of will at all though drop high pian tolerance to 3 health one and put all 3 slots to strength of will with recharges. remove resurgence and get hasten as soon as you can and 3 recharge slot it (you can take one slot from build up and one slot from conserve power which I explain to put where next) instead Willpower is an all around survival set with inspirations you shouldn't die that alot anyway and hasten is just a power you can't skip in katana.
Finally rest;
Get conserve power instead of focused accuracy and 2 slot it with recharge. Katana rarely needs more tohit buff thanks to almost all of its attacks does -defense debuff (and with gamblers cut having defense debuff SO's you don't need anything else if you are not going to put IO sets) and running that much toggle with fast katana attacks will drain your endurance faster than you think.
Fair warning you can't handle things at +4x8 without getting I think you won't have any problem at 0x6 or +1x6 but like i said I didn't played with a katana/WP still with my SO'ed DB/WP I can handle +1x6's in a S/L farm map in AE at level 49 and my kat/SR could handle +3x4 while he was SO'ed.
My alt-itis is acting up again while I wait to play an illusion/time 'troller on live, so I decided to make a scrapper using two sets I've never played before, Katana and Willpower. I made a basic leveling build using SO's to try and figure out how to use the sets. I do plan on using IO's once I hit 50, and I might pepper in some global bonuses before that, but I'm going to be using SO's (or level 25 common IO's) for most my time until then. Anyways, any comments, suggestions, or ideas are welcome.
Hero Plan by Mids' Hero Designer 1.942
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Level 50 Natural Scrapper
Primary Power Set: Katana
Secondary Power Set: Willpower
Power Pool: Leaping
Power Pool: Fighting
Power Pool: Leadership
Ancillary Pool: Body Mastery
Hero Profile:
Level 1: Gambler's Cut -- Acc(A), EndRdx(5), Dmg(7), Dmg(13), Dmg(43)
Level 1: High Pain Tolerance -- Heal(A), Heal(13), Heal(25), ResDam(34), ResDam(34), ResDam(37)
Level 2: Flashing Steel -- Acc(A), EndRdx(5), Dmg(7), Dmg(15), Dmg(43)
Level 4: Mind Over Body -- EndRdx(A), ResDam(11), ResDam(17), ResDam(31)
Level 6: Fast Healing -- Heal(A), Heal(11), Heal(25)
Level 8: Divine Avalanche -- Acc(A), EndRdx(9), Dmg(9), Dmg(15), Dmg(42)
Level 10: Indomitable Will -- EndRdx(A)
Level 12: Combat Jumping -- DefBuff(A)
Level 14: Super Jump -- EndRdx(A)
Level 16: Rise to the Challenge -- EndRdx(A), Heal(17), Heal(39), Heal(39)
Level 18: The Lotus Drops -- Acc(A), EndRdx(19), Dmg(19), Dmg(29), Dmg(42), RechRdx(50)
Level 20: Quick Recovery -- EndMod(A), EndMod(21), EndMod(21)
Level 22: Build Up -- RechRdx(A), RechRdx(23), RechRdx(23)
Level 24: Boxing -- Acc(A)
Level 26: Soaring Dragon -- Acc(A), EndRdx(27), Dmg(27), Dmg(29), Dmg(42), RechRdx(46)
Level 28: Heightened Senses -- EndRdx(A), DefBuff(37), DefBuff(37), DefBuff(39)
Level 30: Tough -- EndRdx(A), ResDam(31), ResDam(31), ResDam(34)
Level 32: Golden Dragonfly -- Acc(A), EndRdx(33), Dmg(33), Dmg(33), Dmg(40), RechRdx(43)
Level 35: Weave -- EndRdx(A), DefBuff(36), DefBuff(36), DefBuff(36)
Level 38: Strength of Will -- ResDam(A)
Level 41: Focused Accuracy -- EndRdx(A), ToHit(50), ToHit(50)
Level 44: Physical Perfection -- Heal(A), Heal(45), Heal(45), EndMod(45), EndMod(46), EndMod(46)
Level 47: Maneuvers -- EndRdx(A), DefBuff(48), DefBuff(48), DefBuff(48)
Level 49: Resurgence -- RechRdx(A)
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Level 1: Brawl -- Acc(A)
Level 1: Critical Hit
Level 1: Sprint -- Run(A)
Level 2: Rest -- RechRdx(A)
Level 2: Swift -- Run(A)
Level 2: Health -- Heal(A), Heal(40), Heal(40)
Level 2: Hurdle -- Jump(A)
Level 2: Stamina -- EndMod(A), EndMod(3), EndMod(3)
Level 4: Ninja Run