Gallade: BL
Why has the hype died down?
The reason all the Gallade hype has died down is not because Gallade is no longer broken, it is because people just stopped using certain Pokemon which have become liabilities in the Gallade metagame. For example, it's easy to notice Gallade merely being at #8, but the fact that Pokemon such as Milotic, Chansey, and mostly Registeel usage has gone down drastically is a clue that Gallade's usage is merely suffering because people tend to just not use stall-based teams anymore.
For example:
Let x be a Pokemon that makes Y useless / not viable, but x has no effect on Z.
Y usage is normal at the beginning, so is Z usage. People realize they can completely reliably beat Y teams by using a team with x in it. So, people start using Zx. Consequently, Y users realize "Oh wow, I can't win regardless of what I do when someone uses x", so they switch to Z users. After this, Zx users realize there is no Y teams to "automatically beat", and while x isn't "bad" against other Z teams, there are still Pokemon who function even better against other Z teams, so x's usage goes down.
It's pretty clear that x is Gallade, Z represents non-stall teams and Y represents stall teams.
Why is Gallade broken?
Gallade is one of those Pokemon who people will always say "prepare more" when refuting a claim that Gallade is broken. This is because Gallade will not often completely "sweep" a team if you are using an offensive team made with 4-5 checks. This completely misses the point, in my opinion. First of all, with Gallade, stall is completely useless. Gallade fulfills the offensive characteristic against all stall-based teams, and people should not be forced to play balance or offense. Second of all, Gallade has no counters. Zero. Nothing can safely switch into Gallade in this metagame. I'm sure you don't need me to copy + paste the calculations from the Gallade thread, but the only Pokemon who can actually deal with Gallade is non-existent due to being the only effective Froslass counter and needing 176 Atk EVs to do so (Spiritomb). Arcanine does ok, but when there are so many entry hazards in this metagame, Arcanine only switches in with 50% HP, which frankly isn't enough to stop Gallade.
I'm not exactly clear on which characteristic this puts Gallade under, since "not having one safe switch in, and being able to sweep a team not made up of 6 fast normal types with little effort" isn't the clearest of statements. I'd probably lean on it being broken on the offensive characteristic, since when against certain team-types it sweeps with little effort. Against balance teams it would probably fulfilling the support characteristic since it OHKOes everything, making it too easy to sweep. In layman terms: Gallade fucks up other 'mons with little effort.
Now this wouldn't really matter if Gallade was a liability against Offense, similarly why Blissey and Chansey aren't Uber or BL respectively for easily beating certain types of Pokemon or teams. Gallade is far from a liability on offense, however. With 284 Speed, Gallade ties at worst with other base 80s (who are forced to run slow spreads most of the time, unfortunately), and simply outspeeds a good chunk of the tier. Better yet, Offensive Pokemon have trouble switching into any sort of attack from Gallade, considering that it can OHKO the entire offensive metagame. No offensive switch is safe.
Gallade hits far to hard for this tier to handle, and it isn't easily stopped due to its priority attack OHKOing a chunk of it's revenge killers (all Ghosts, Dugtrio, Psychic-types) and excellent special bulk. It has decent Speed as well, allowing it to beat out many of the more commonly used Pokemon in UU.