if your not the lowest in lfr it means it is viable. but you should stick to some random bg and dungeon. sure no raid leader will take you as dps. but random dungeon lfr and heroic will be done as shockadin.
http://dictionary.reference.com/browse/viable
viable means capable of living. and if your not the lowest on the dps list it means it is viable.
is it going to be a real dps spec? no. but we didn't ask for it. we asked for this fun spec where we could kill undergeared players.
same as demo warlock tanks will be viable when you make content to easy. so if you want it to be non viable. just increase the diffeculty of the content.