The Gearhulk cycle looks slightly uneven at first glance. The White one looks like the strongest, followed by the Red one. All have Enters the Battlefield (ETB) abilities.
The artifact theme got a Mythic Rare, and so did the Vehicle theme. Esper got all the Mythic Rares, and then we have Rashmi (love this card) in Blue/Green.
A fall set with four planeswalkers is almost a core set. I wish they would bump these sets up to five, but that's just me-I love planeswalkers.