Yeah I have to jump on the Naive / Superpower boat too. It makes Tornadus-T very difficult to dance around, and since Tornadus-T by nature likes to switch out often, the stat drops are rarely much of a downside. The boost to U-turn from running Naive instead of Timid is just a nice little bonus.
As far as the fourth moveslot goes, I'm surprised Hidden Power Ice isn't seeing much discussion. It smashes Choice Scarf Thundurus-T trying to switch in to tank Hurricane, and also smacks Dragonite, etc. Taunt is also a pretty cool option, though I expect its utility against Ferrothorn to decline since Gyro Ball seems to be looking like a more and more appealing option with Tornadus-T, Breloom, and others running around.
As far as the fourth moveslot goes, I'm surprised Hidden Power Ice isn't seeing much discussion. It smashes Choice Scarf Thundurus-T trying to switch in to tank Hurricane, and also smacks Dragonite, etc. Taunt is also a pretty cool option, though I expect its utility against Ferrothorn to decline since Gyro Ball seems to be looking like a more and more appealing option with Tornadus-T, Breloom, and others running around.