Aggron's had a nice run in RU, but it's time for him to come home. Sand teams are still doing their thing, and many people forget to pack a Stoutland check or get their Rhyperior worn down too quickly. The big mineral dino has a much easier time coming in on both Return and Crunch, and takes 28.5% - 33.8% from Wild Charge at worst while Rhyperior has to worry about lucky crits or defense drops on a bad day.
Those who have played him any this gen or last knows what's gonna happen when he starts busting out CB Head Smashes, but another thing I was pleasantly surprised about is how effective Heavy Slam is as a secondary STAB; Hitmontop, a formerly decent counter, can't switch in on one of these to save his life and neither can Hippopotas. I was even tempted to use Heavy Metal on him once but it's not released and Heavy Slam caps at a disappointing 120 BP.