In general, Fly is a pretty bad move, because it basically the gives the opponent a free turn, so no I wouldn't call that set viable. In addition, movesets are more or less coverage against various Pokemon - having perfect coverage doesn't necessarily mean it's good, as it still misses out on certain Pokemon - for example using that set, Landorus loses the ability to beat Fairy-types such as Clefable because it lacks Sludge Wave, and the likes of Garchomp, Gliscor, and Landorus-T because it lacks HP Ice.