Ground Arceus, particularly special sets (A special set isn't even a main set though...), do have some flaws; it has a hard time against Pokemon immune to Judgment, such as Ho-Oh, Latios, and Latias. Furthermore, it lacks the power to break through specially bulky Pokemon, and it has redundant synergy (offensive or defensive? If it's both, just use type synergy) with Primal Groudon. Luckily, the better and more common Swords Dance set can smash some of the checks to the special set, giving Ground Arceus a fair bit of unpredictability and very few safe switch-ins (But SD is its only main set, so won't opponents prepare for it?). Pokemon such as Choice Scarf Kyogre and Grass Arceus are less uncommon as well, allowing Ground Arceus to be even deadlier.