Not that there IS much variety at the top of the DW ladder, but it's not so different from OU, which doesn't exhibit variety either. In general, there is more variety in DW because there are no voting reqs so people are more willing to try out new things without risking their rank from dropping.It's also a broken tier where everyone uses Rain.
Lets face it, there isn't much variety. Even Sand fails here thanks to Keldeo raping everything, allowing Rain to...reign supreme.
Now you got Latios spamming +1 Attacks all over the place and then comes Genesect to counter him, but then comes Chandelure to trap him.
Everything revolves around Latios, Genesect, Politoed, Chandelure, Keldeo, and Ferrothorn.
Keldeo is good against a lot of Sand and Rain users, but ever since Soul Dew Lati@s was discovered to be legal, it's really not so great. Those two don't take much damage even from +1 HP Ice, with Latios taking a maximum of ~55% in my experience, while it does like 90% back to +1 Keldeo with Thunder. Ferrothorn also gives it a lot of trouble.
What you've said about revolving around this set of Pokemon is true, but how is that not the same in OU? Everything revolves around Tyranitar, Politoed, Scizor, Excadrill, Rotom-W, Ferrothorn, and Latios.