No idiot. While all commons have to be low complexity cards not all simple cards have to be common. Griselbrand is a very simple card. As it's Avacyn.
New World Order
Adrian Hughes
Joseph Russell
Blocks can shift color identity. It has been repeatedly said by Mark that in Innistrad black bleeds into other colours, so that black effects can appear in non black cards.
James Nelson
Not *all* commons necessarily have to be simple. There can still be some complexity at common, they're just careful with it. Ghostly Flicker is a straightforward card to experienced players, but it's super complex to a newer player because they have to learn that
1. It re-enters without any counters it had, and any "until end of turn effects" are also gone
2. It re-enters untapped, even it was tapped before, but this doesn't count as actually untapping it
3. It re-gains summoning sickness, if applicable
4. It triggers ETB effects, both its own and others'
5. Any spell on the stack targeting it fizzles, saving your card from damage or "destroy" effects, although...
6. Wrath effects or "damage to all creatures" effects still hit it, since they don't target
And you're potentially having several of those cases come up at the same time. Twice. And yet people complain that NWO's reduction of complexity at common has dumbed down the game.
Ethan Moore
New World Order doesn't really care if something is mythic rare or rare when it comes to complexity.