>>40749804Tyranitar has a 600 BST to work with, automatic sand for a +50% Special Defense boost, a typing that doesn't make it x4 weak to Grass-type moves and Hot Water of Skill, and an amazing movepool. Every other non-legendary, mythical, or Ultra Beast Rock-type suffers from some combination of poor stat management, useless abilities, poor type combination, and a very limited movepool.
A good example is Gigalith. Gigalith's stats are pretty good, and it even has Sand Stream like Tyranitar; however, it has almost no moves. Another example is Aggron, who has a ridiculous movepool not unlike Tyranitar, but can't make use of most of it because its poor Special Attack, and roughly a third of its BST is taken up by its Defense. The Rock typing itself is an issue, as well: A Fire resistance is nice, but Flying is rare outside of STAB, Poison is terrible offensively, and Normal is never used except for STAB. For this, Rock is weak to Fighting, Ground, Water, Grass, and Steel, the first three of which are very common attacking types. One of Mega Aggron's biggest improvements was removing its partial Rock typing, as it was impeded its ability to take hits by giving it more weaknesses without really gaining anything other than removing Steel's Fire weakness.
