Ok, this is just a personal thing, and others may just stand back and laugh, but I build my scrappers (all 5 of the deranged little mob mashers) with survival as the main focus of the early levels.
Granted this sometimes means they have few attacks early on, but it also means they stay standing long enough to use the attacks the do have a lot more than those with more attacks. You can't hit anything if you're laid face down in the dirt after running out of End or HP.
I'll slip Build Up in at 22 for my BS/Regen, I found Quick Recovery far too important to skip. Granted Katana does use less End per attack, but with the faster recharges and lower damage you'll be swinging more so kinda evens it out a little.
Moral of the story, grab QR asap, it'll allow you to push Stamina back until the 30's (lvl 30 for my guy to be exact) and allows you to free up a few early power choices which you wouldn't have if you crowbar Stamina in at 20.
Just my personal view, living longer is better than more hitting stuff powers, and as */Regen, you don't NEED Stamina at 20.
Thanks for that, it made sense, and helped. 
Katana is cheap primary, you'll be fine with QR, can drop stamina until 30's, and won't really need it even then, unless you don't want to slot EndRdx in attacks, or want to run FA.
I agree with others. Take quick recovery as soon You feel the need. Then take stamina later when You get more heavy endurance cost attacts and toggles. I designed to take QR at level 8 and stamina at level 30.
Right, on my Katana/Regen I took reconstruction at 4, then BU at 6 and Divine Avalanche at 8. Now I have every intention of fitting in Dull Pain at 10, but where do I put Quick Recovery? I want a travel power, want Stamina, but I want this as well. According to the character planner I have Quick Recovery has a higher end recovery than Stamina, should I not bother getting Stamina?