The DPS difference between the three ranged specs is not some ridiculous shortcoming for sorcs as its a minuscule difference between all the ranged classes. Obviously theres a much larger gap in the ranged vs melee discussion but that wasn't your original argument. (Which im not saying I disagree with, but to say that was your original argument is false)
To say any class isn't viable is disingenuous to the rest of the community, if someone wants to play a sorc dps and can pull competent numbers then all power to them. There isnt enough of a difference in dps/raid utility/defensive cd's to suggest otherwise.