Although I am still undecided at this point and do think that pokemon0078 does bring up some valid points, I do want to say that those solutions are viable but other than that they are rare and don't have too much other use because of the condition of the current meta. Blissey / Chansey are obliterated by the swarm of powerful physical hitters- Kyu-B, Fightings, Lando-T, Dragons, they are all powerful enough to break down the two walls. Skarm is on a similar boat. Deo-D is a much better fighting type counter, and now many Dragons carry coverage against Skarm, also degrading its niche. Rain is still going strong, and Surf spam from Keldeo certainly isn't helping. Sun is not used much anymore either, because Rain / Sand are getting just too powerful. Of course, I love me some SpDef Ninetails to counter Tornadus, but due to the fact that most Rain teams carry numerous answers to Sun as well as SR Ninetails just doesn't get as many chances to switch in anymore.
The list of common counters to Torn-T is not long- but I think its list of checks is more similar to that of a solid OU pokemon. LO Latias rose up to the stage to be a good check; it can take a hit or two, Roost of the damage, and the hit hard. Most common Scarfers can take a hit and KO as well; Scarf Latios is certainly capable of doing this, LO Hurricane will never OHKO Terrak even outside of Sand, and Specs only KO's 1/3 of the time. Thundurus-T is a lesser known but still effective check, as it can take a hit and reply back with VSwitch or Tbolt.
The thing with Tornadus-T is, you have to play your cards right or it'll rip apart your team- and many successful Torn players I've seen win by removing Tornadus-T counters and then sweeping. The problem is that true counters are rare and checks often are weakened and can't handle it. Either way, Tornadus-T is quite dangerous.