Notching Rafters for wires to res
No, it's not. You'll weaken the rafters.   Edge cuts are particularly harmful to structural members.  

If anything, you would rip a whole bunch of shims, (say, 7/8" thick), and lay them across the tops of the rafters, omitting them where the wires are.   Or sister the rafters. 


However, this would create a second code violation: wires too close to the floor surface, and vulnerable to being nicked by nails.   This can be remedied by putting steel "nail plates" above the wires to guard them from nails up to 1-3/4" long.  However it wouldn't be enough to protect only above the rafters, because the cables are being drawn taut between rafters, so they are vulnerable there too, especially near the rafters. 


Stapling the wires to the rafters and using sufficiently thick shims would take care of that.



You're also not allowed to cut the -- well, hold on. You're not allowed to cut the cables and then make a desperate, taut splice with what little length remains.   You are allowed to cut, reroute and splice additional length in the middle.  However all splicing must be inside junction boxes*, and the boxes must remain accessible forever.   I recommend large-ish steel boxes, because if you do have a bad connection that arcs, the steel won't melt and burn through, and will distribute the heat around the entire box, reducing the chance of any point turning hot enough to ignite building materials. 

Steel junction boxes, plus non-flexible metal conduit (EMT, RMC or IMC) are a great way to make the "shim" strategy actually work.  Now the shim needs to be no thicker than the pipes, i.e. 7/8".  These tough pipes are their own nail plates, taking that problem off the table. Inside the conduit, you'd use THHN/THWN-2 individual wires; up to 4 circuits per conduit pipe. The pipes are also their own grounds, meaning no need to push ground wires through the conduits.  Most circuits only need 2 wires, and the 1/2" trade size of these pipes can support 9 or 10. 


There's no profit in using 3/4" pipe.  You could use 1" pipe and put up to 10 circuits in a pipe, but the wires in the pipe would need a wire size "bump", 14 AWG cable -> 12 AWG THHN, 12 AWG cable -> 10 AWG THHN. In those cases I prefer to lay two or three 1/2" pipes, especially if bending is involved. 




* If you ask how to splice without a junction box, the Home Depot clerk will cheerfully press one of these into your hands.  No mention will be made of the fact that these are illegal, except in very particular applications.  These are the same dim-bulbs who will cheerfully recommend a NEMA 10 dryer outlet "since it's universal".