well, as Nom said a little while back:
In SoO, if you enable smart taunting and the tanks are properly marked as tank then it should taunt at the correct stacks for you . Do not enable auto taunt, thats for farming

.
I've never really used it, as i prefer to do the taunting myself. But i havent really heard anyone complain about the feature.
"SoO Flex/Norm Tank Switch Cheat sheet"
Immerseus: Switch on one stack of Corrosive blast.
Norushen: Switch on whatever you and your tank partner feels comfortable with (usually somewhere between 3-5).
Sha of Pride:
As soon as Wounded pride is cast on your parter.
Galakras: adds in the early phase doesnt really matter as long as they are on one of the tanks. Just switch at 4 on galakras himself.
Iron Jug: Switch on 3 stacks of ignite armor (protip; run to the first bomb, charge the second and the third and then Heroic Leap back near the boss, so you're ready to pick it up once your off-tank hit's 3 stacks)
Shamans: Switch on 5 stacks of Froststorm strike (if you're doing HC, you should look up some of the various strats)
Nazgrim: Switch at 3 stacks of Sunder, otherwise he's gonna get a shit-ton of rage, and thereby a shit-ton of ravagers
Malkorok: We usually goes for about 16-20 stacks... It lines up quite nice with two smashes btw
Thok: 3 Switch at 3 stacks of Fearsome Roar -> 3 Stacks of Acid Breath -> 3/4 stacks of Freezing Breath
Siegecrafter: Switch on three, go out and handle shredder while you're not currently tanking (ez pz)
Paragons: Dear god... Look it up somewhere else... it's piss easy to do. But extremely complex to explain. Just keep an eye out on your debuffs
Garrosh: If you're tanking garry in P1, you're gonna get the adds... theres hardly a way around it. In P2/3 you'll usually just switch at around 5 stacks or so (they stack up quickly, keep taunt ready for this).