As much as I enjoy nitpicking and biting sarcasm, particularly the implying that Garchomp is so physically broken (via the Groudon comparison) that it doesn't need any power on the special side, Salamence has more base Attack than Garchomp too. 
		
		
	
	
 Groudon is also far more bulky than either and, clearly, more people should use CB Salamence.
The entire point of defining most of the Base 100 pokémon as defensive was that Garchomp's Speed 
doesn't eliminate an additional six OU pokémon from revenge-killing. For example, it doesn't really "eliminate" Jirachi from the list. Jirachi rarely runs max Speed, so Salamence is hardly more at risk of a revenge kill from it than Garchomp ever was. 
(The actual risk is that Jirachi can take a hit from Salamence but Garchomp OHKOs. :P Perhaps Calm Zapdos is a better example here.)
Regarding the last two paragraphs, Tyranitar is excellent set-up bait itself (CB Pursuit) and killing most fast revenge killers would also benefit other set-up pokémon in this speed range, like SD Lucario or SD/NP Infernape. 
(Hell, some people use those "Pursuit bait" pokémon specifically to give SD Lucario opportunities to set up.) Magnezone also removes basically every check (read: Steel), sans Heatran who only checks Choice sets, for every Dragon. Building part of your team around a particularly strong pokémon is very common and Garchomp certainly isn't the only sweeper used in that vein. (On the mention of Hippowdon, it's a pretty good Garchomp check itself.)
Now, to be serious, it is certainly a handicap in having to use Tyranitar or Hippowdon along with Garchomp. The fact they're good pokémon in their own right minimizes the disadvantage you receive from being pigeonholed into using one of them but it doesn't change the fact you do. 
(Well, you don't have to use them, but then Garchomp's one decided advantage over other sweepers goes unrealized.) Beyond the actual pokémon one is forced into using, the mere presence of Sand Stream forces one to build the other four pokémon around it. Life Orb usage becomes a little dubious, more EVs will go to defenses over HP as SS nullifies Leftovers recovery, and so on. Building around Garchomp is a lot more restrictive than building around any other sweeper, is that worth the extra "oomph" every fifth game?
EDIT: In attempt to stay on-topic, i.e. help decide whether the named Suspects belong in the Uber or OU tier 
based on evidence over theorymon, I should probably answer my own rhetorical question. No, I have not been particularly overwhelmed by Garchomp any more than various other sweepers. The way my primary Suspect team is built, I actually have more trouble with Heatran than anything. (Gyarados too, which I half-assed remedied by sticking Tbolt on half my team. :P) Obviously, defending against all threats is impossible these days, but I didn't have to dedicate half my team specifically to countering Garchomp in order to handle it. I do quite well against it, or at least as well as I can alongside the Latis too. (Dragon overload -_--------) Every team has their trouble opponents and I'm sure Garchomp is on many of those lists but I haven't seen evidence that's it's remarkably stronger than many other potential candidates.