Ok, specs Gothitelle is broken IMO. It allows you a foolproof way to break through an offensive pokemon's select counters. Without their Hitmontop or Gligar, many teams struggle against Hera. Without Suicune, Milotic, or Slowbro, what can switch into CB Darmanitan? You have an almost risk-free way to secure a kill on a group of walls (or simply threaten it to scare them out of going into their walls. Under the support clause, this thing is easily broken. Moreso it makes stall and semi stall essentially unplayable because defensive cores can be broken down incredibly easily, which drives the metagame to highly offensive play and limits the diversity in Pokemon and play style that makes the UU tier what it is.