Question

Can you catch any of the forms of landorus, thunderus and tornadus in dream radar?

Answer 1

No, you only get the Therian forms.

However, If you take Landorus - Therian to the Abundant Shrine, you get an item called Reveal Glass. With this, you can change their forms at any time.

Answer 2

You can catch the new Therian forms of Tornadus, Thundurus, and Landorus, if that is what you mean.