You may rather see the same cycle of guys, but aside from Orton and Cena all of the guys that have been staples of the WWE for most of the last decade are all on the tail end of their carrer. They need to build up the next generation. Miz and Del Rio are far from jobbers. They get reactions, granted not nearly the reaction that guys like Cena and Orton were getting during their initial push, but here's the thing: hardly ANYONE gets a huge reaction, aside from Orton and Cena. Miz and Del Rio both have been pushed pretty heavily for the last year, and it's pretty obvious that the WWE is banking on them being two of the top guys for the WWE for years to come. And when it comes to doing nothing before being given the title, nobody trumps Sheamus. The Miz before cashing in the Money in the Bank was easily the hottest thing in the WWE, and unless the WWE wanted to pull a TNA with Samoa Joe situation they made the right move. Del Rio also has been one of the focal points of Smackdown the last few months. Hell, not many guys upon debut are thrown into a program with the top face on Smackdown (and arguably the company) and 'put them out'. So what if Del Rio hadn't been in the WWE for years? It's not like he's straight out of wrestling school, he taken years 'paying his dues' in Mexico, I wont go as far as to say he's a best in the world type of worker, but as far as WWE wrestlers go, he's IMO one of the better ones. Much like the Miz he has what it takes; charisma, mic skills, and in-ring ability (yes the Miz is a good in-ring worker, not a HBK or Cena ring general, but he is pretty good)
edit- is it just me or does the term 'jobber' get thrown around way too fucking much (Not excluding myself)?
cough cough: see the Miz MARK above.)