The guy looks to me like a Kevin Gregg clone and significantly inferior to Dotel. He also has a significant injury history. He missed all of 2004 and significant parts of 2007-08. So why is he regarded as being on a level above Dotel?
I think one of the main reasons, Wilbur, is because Rodney has experience closing for a contender. Including 4 appearances in the 2006 WS. GMs of contending teams know that Rodney can handle the highest-pressure pitching situations - he's proven so. So, they become willing to pay Rodney - and pitchers like him, such as Valverde, who pitched in the 2007 NLCS - a premium for that experience.
GMs of contending teams usually want to go with "known" players, who've been through the grind of a pennant chase, before. At least that's my thoery on the matter.