also worth noting that in one of the generations that I think one could easily argue has metagame balance issues that should be handled via tiering action (gen 7) the most used mon (lando-t, naturally) has about 40-50% usage (depending on what you pull from, varies. spl has 50% for instance). if you look at all the things that one could reasonably consider 'broken' or worthy of tiering action in kartana, magearna, ash-greninja, possibly volcarona (a huge stretch), lando-t doesn't answer any of these almost at all. It can help awkwardly pivot around kartana and av magearna but that's far from the main methods teams typically want to use to handle these threats (see: one of the most common defensive structures for BO is lando+torn-t+av magearna). While these numbers aren't quite as high as tusk is, they definitely show that pokemon can be extremely common while not necessarily being a response to brokens.
Great Tusk is simply gen 9's new landorus-therian, an excellent option for defensive and offensive role compression with a myriad of good sets, but certainly not broken or a herald of broken elements in the metagame at large.
(also for usage stats the
showdown ladder usage stats and
spl usage stats are your friend, and typically other large tournaments will also have similar threads. willing to give advice on how to use/interpret if you like. there's also various third party websites that unofficially help visualize, but they tend to be a bit out of date at times)
It's also probably worth noting that pre-espathra ban statistics reflect a different metagame for what that's worth