Excadrill has a lot of counters, checks, which is why he remains in OU. Let me list them all.
1.) (Politoed/Ninetials) Ninetails is 2HKO'ed by LO Excadrill's earthquake IF Ninetials holds the Shuca Berry. In all honesty, a lot of things use earthquake on Tails, and when the suns up it should outspeed it anyways, and you can proceed to Will-O-Wisp
2.) Hitmontop should be able to take a hit, especially if you pull off an Intimidate. Close Combat, Mach Punch? Sure he can switch out, but you can't ban a Pokemon off other Pokemon teamed with it. Its your job as the trainer to play around his team and take out Excadrill.
3.) Gliscor
Lets see, rock slide/x-scisspr/rapid spin will not do a thing. Excadrill will probably try to pull of a SD, so just play offensive with EQ. It should be like between a 2HKO. I haven't done the calculations, but I played enough around Excadrill to know a range.
4.) Dusclops
This thing is never mentioned. It does way better than sablye, as it can probably take more than 2 hits and he can fire off Will-O-Wisp and cripple Excadrill. Pain Split? Brick Break? NIght Shade? This thing can play around Excadrill, and since hes "always switching" he can't keep the SD boost.
5.) Skarmory
Honestly, it can't get that many flinches everytime. It can abuse roost and make anything Excadrill throws useless. Set up spikes, use roost, brave bird balloon (if any), whirlwind spike spam.
6.) Dusknoir
No need to explain, bigger version of Dusclops with a few defense drops, gains of leftovers, and bigger power boost for Brick Break.
7.) Donphan
Donphan can usually take a hit, fire an Earthquake, and even fire Ice Shard before death.
8.) Sablye
He can fire Will-O-Wisp on any physical sweeper. With some blissey/chansey support this thing can actually be a real threat in OU. I do admit that special attacks dent him, which is why dusclops can prove better.
9.) Rotom-W
Levitate, it can probably take one rock slide, and trick. After you trick it choice specs/scarf, this thing is really useless as it has to switch everywhere. Will--O-Wisp on the switch (its natural special bulk can prove usefull) and work your way around Excadrill).
10.) Conkeldur
It can take one earthquake, and hit hard with a Drain Punch, gain most hp back, and proceed to Machh Punch. Play around sand team, and the rest is history.
11.) Infernape
SashApe can close combat and mach punch FTW. Matter of playing around his team. It works well when your opponent doesn't predict the sash and kill.
12.) Azumaril
Banded Aqua jet, it can OHKO or 2HKO Excadrill. The Problem: Its obvious. Takes a lot of skill to use this one, but it can work.
13.) Swampert
It can take any hit, and counter with scald/surf/waterfall/earthquake. No reason this isn't a good counter against Exca
14.) Suicune
Suicune should be able to take Earthquake (non-life orb, not sure don't have a damage calc) Scald/Surf/Hydro Pump
15.) Whismicott
Cotton Guard Whismicott? 3-4HKO on air balloon Excadrill. 2-3HKO LO Adamant Excadrill. 5HKO with +6 vs regular excadrill. So, this thing can do a pretty good job leech seeding it. It can stall it out, ive seen momento sets, which can work when hes the last pokemon
I think there are a few more, can't think of atm. Oh yeah, sash Alakazam.
1: Ninetails/Politoad: Excadrill switches out, Tyranitar comes back in. Your weather inducers can't take a 2nd hit later.
2: Hitmontop loses. End of.
3: Why do you think Gliscor is #4 on the ladder?
4: Dusclops kinda sucks, and it has to take two Earthquakes, so will be completely crippled.
5: Skarmory is only a check. It takes an attack as it switches in [Good Excadrills will not EQ while Gliscor/Skarm are around], it then takes another as it Whirlwinds.
If Skarm brings in something it can't Roost on, gg, because it won't get a second chance. Flinchax is a possibility to.
6: 2HKO'ed on the switch
7: 2HKO'ed, and, Air Baloon?
8: Sableye can't switch in, and Will-O can miss, so you shouldn't rely on it.
9: Rotom-W loses to Return, and X-Sissor and Rock Slide do numbers on it too. Hydro Pump could also miss.
10: Conkel cannot switch in, and Mach Punch can't OHKO without a Band/Guts boost.
11: Sand is up, so how does Sashape survive to Mach Punch? Also, hazards. Also, how does he switch in?
12: Can't really switch, in, is blatently obvious about what it will do, so you switch out.
13: Can take any hit. Once. It cannot switch in. If it tries to revenge, Excadrill switchs out
14: Can't switch in.
15: When are you getting to set up two Cotton Guards? Also X-Scissor, and what can you do back?
So, basically, those 'checks' and 'counters' you described... 90% of them can't switch in, and all but one is a shaky check at best. [Gliscor] Some of them aren't checks at all, such as Dusknoir. Also, none of them stop Excadrill going away, and coming back in later once the obstical has switched out. Oh look, that's a 2nd mon you've had to sac! Then a 3rd!
