Shall not post a TL;DR.
Okay, to start off Excadrill completely overcentralized the metagame. First off, It made scarf Pokemon completely useless since nothing could reach Excadrill's speed. You basically have all of these Pokemon sitting around the 346 to 352 speed stat, and then there's Excadrill sitting at his impossible to reach 604. Nothing can get to that point other than ScarfPolitoed by removing the sand, Deoxys with a scarf (lolololol), and Priority and the only things that can OHKO Excadrill at 100% with priority is Azumarill (99% of the time, the other 1% it'll live with like 1 HP), and Guts boosted Conkledurr ... all of which you need to sacrafice something to bring in, whereas Excadrill can just switch out like no man's business.
Another way it overcentralized the metagame is by ruining so many playstyles. Hyperoffense had nothing that could stand up to Excadrill, other than Conkledurr and Azumarill, both of which you need to sacrifice something to bring in, or ScarfPolitoed, who ruins your chances of running fire-types. Pure Stall is completley screwed by Excadrill:
Pure Stall: "Hey, my name is Pure Stall and I just set up all three hazards"
*In comes Excadrill to spin away your hazards because no spin blocker would dare switch-in on Excadrill*
Excadrill: "Problem stall?"
Excadrill is free to switch-in all he wants on your stall team since he can pretty much live anything you throw at him because he also is pretty bulky. The fact that he can also run Air Balloon to lol at your Earthquakes and get in another SD just makes him even more amazing.
The final way he overcentralized the metagame is by forcing you to run either Skarmory, Gliscor, Bronzong, or Tangrowth on your team to counter it. Of those Pokemon, the latter of which get Stolen by a +2 X-scissor:
+2 252 Atk Adamant Excadrill vs 252 HP / 80 Def Sassy Bronzong (aka standard Bronzong): 47.9% - 56.2%, so you need to keep Bronzong at full health just to counter Excadrill. That's no easy task considering you don't even have reliable recovery.
+2 252 Atk Adamant Excadrill vs 252 HP / 252 Def Relaxed Tangrowth: 60.4% - 71.3%, yeahhhh, so much for that.
The only things that can reliably counter Excadrill is Gliscor and Skarmory. You're pretty much forced to run Gliscor on your rain team, unless you feel like sacrificing one of your Pokemon just to bring in your ScarfPolitoed. Skarmory can't even threaten Excadrill outside of breaking the balloon and phazing it, and it looses if Skarmory is your last Pokemon left. You can't even put Skarmory on a rain team because it gets no gains from it, and it absolutely fears the thought of a high-powered Water-type move. Skarmory is like ocd when it comes to what weather is on the field. Did I mention Gliscor has a Water-type weakness? Because it does and rain just makes it worse.
Have we gone over sun yet? Nope? Okay then, let's just go off and say that sun has only one thing to deal with Excadrill and that is 164 Spe Timid Ninetales who can't even switch in because of that typing. This means you have to sacrifice something just to bring in Ninetales, thus taking in hazard damage. Then Excadrill switches out to lol at your recent move. Now you're loosing because that was the only move you could make to not loose right there.
These are all reasons why Excadrill overcentralizes the metagame, which makes it a textbook definition of being broken. The reason why things like Volcarona, Dragonite, Salamence, and Latios don't overcentralize the metagame is because you don't see them forcing you to run a certain Pokemon on your team, or completely ruining a playstyle just because this one Pokemon exists.
If we keep going like this, I'll have to rename this thread
The Blaziken Thread v2. Yes, I will go there.
And an image to go with my post so it isn't all srs srs srs