While SM has been buffed to something great in 0.9.9.7, I really hate picking reloader, especially now, with the ridiculous ton of ammo boxes randomly dropped (or in crates, or randomly found in military base's crates, or in new specials...)
In other words, I don't want to put 3 levels for just SM.
My current builds are rather focused on SoB 2 or 3, which are just insane. Won my 1st N! game with, probably SoB->Int2->Sob3, and it looks like the easiest build to me atm (while MAc is, of course way more efficient if you got enough skill to live without Int2, but ammo is a negligible problem for me. A few shell boxes are enough to ensure you'll have enough.)
I don't pick juggler either. It's OP, of course, but I just rarely want to "waste" a level for Jug while I need a mastery, 4 levels for WK, 4 levels for SoB, some EE and HR.
The other skills seem quite pointless to me. Iro slightly reduces YASD risks, TaN needs to take damages, which is not the best way of planning to play unless you're melee, and Fin is mainly necessay for WK (Well, Fin3 is great, I always pick it at clvl 12, but 1st lvl are really weak compared to SoB or EE, in term of DPS).
SoG and Bru are just build-specific.
Same applies to the masteries :
Melee masteries are great, since melee is OP
Gun kata isn't bad, but "blocks WK", and BD seems useless, so I only consider MSS
Shottyhead blocks SoB for nothing. Fireangel, at least, gives something useful... but not necessary at all, so I wonder why I would build it outside of the MockRL module. MaD blocks WK, but gives a serious compensation.
MEn seems useless. MCe and MAc are OP.
Scavenger doesn't weaken your char but is only good for Ao100 or technician badges. Survivalist is useless, and gurunner... blocks WK and SoB, doesn't work with game's best weapons, and has no effect when not running. Tried it once for AAoRa, and discovered that SM wasn't in the prerequisites... Needing lvl 9 to become operationnal, while I can be at lvl 2 with SoB, seems ridiculously weak to me.
In other words, I only really consider MCe and MAc, plus MSS, MAD and melee masteries (but I hate restricting masteries, so I don't wanna suck with non-gun or non-melee weapons, or have WK blocked).
MSc is very specific to challenge or assembly hunt, but doesn't really help you to win the game (unless you want to disassemble and early Trigun, but I'd prefer switching to gun build and/or try a Klear cross)