I'm not sure The Clone Wars actually qualifies are EU because it's entirely official and is part of the main story.
I should also say that I think season 3 is when it starts getting good. 1 and 2 are a bit pointless, shorter less cool plot arcs.
the clone wars is George canon, it is not EU. Its basicaly at same level of the films canon wise.
I enjoy the series, actualy. But i dont see how it has anything to do with SWTOR.. swtor is Old republic, diferent timeframe. The KOToRs would be a better source though.