I've been playing Skaven for the better part of a decade and I've only seen one SAD army, and it wasn't even my own.
I'm not into grand tournaments, so I have a big blind spot there, but to be honest I think a lot of this SAD talk comes from people on the internet who've heard about it and seen army lists but rarely if ever fight Skaven. A lot of Skaven players have a preoccupation towards Skryre with the new book. It's only natural I think: it seems powerful, and cheaper than pure horde to build, and the tactica at the back of the book blatantly suggests you go for it. You can do an incredible amount of damage just with 'twins' and a pair of ratling guns, but that doesn't make it a 'SAD' army, which would have purely caster heroes, big units of jezzails and multiple small clanrat units to act as ratling gun caddies.
My early Skaven armies in 6th, which leaned a bit that way more than now, could get off a couple devastating, memorable casts/volleys--but they were not nearly as effective at getting a victory as a large force of clanrats and slaves arranged in checkerboard, flank denying formation.