Meh, banning Excadrill really wasn't worth it imo. Quagsire nicely says hai to such rubish and trolls, same with Stockpile Gastrodon, and to make things in the least bit worse for Exca, you got prioirty WoW from the now-released DW Sableye. Oyah, for luls +2 X-Scissor from Excadrill is the only way to 2HKO Eviolite Tangela.
As for my opinion on Thundurus it is this: Although my experience with Thundurus is usually positive, I normally see him die far earlier then most Pokemon on my team. Even though Thundurus manages to cripple/take out atleast one Pokemon, he dies somehow to the next Pokemon out, and has problems with common Pokemon such as Nattorei and Heatran, only really being able to Taunt out Nattorei, whilst being stalled out just from it's steel typing. same with most Heatran. If it was my vote that counted I'd keep him OU. He isn't really gamebreaking and just because you have priority Nasty Plot/Sub (as most complaints I've seen) doesn't mean your the best/one of the most groundbreaking. On the support side of Thundurus, if your so worried about your sweeper getting paralyzed before it can do anything, get a clearic/Blissey/ Status Absorber/counterer. For a check, I've been finding Scrafty to be effective, running Shed Skin, but this is just a suggestion, reguardless, I haven't really had many problems with opposing Thundurus, being able to take them out fairly easily.
tl;dr version: Thundurus isn't as Uber as it seems imo
/my 5 cents