His CV should have nothing to do with how we have viewed his tenure as England coach. I have tried to refrain from entering these debates as too many people in my opinion are unable to change their prior conceptions and opinions on people. I personally didn't like McNamara's selection as England coach but he has changed my opinion. He inherited a pretty dire England set up and has fundamentally changed that and the playing style of the team. In 2011 and 2013, I have seen an England side that has defensively improved dramatically but has also severely trouble the Kiwis but more importantly the Australians in attack, getting outside both teams on the fringes and scoring consistently outwide. We haven't done that since the early 90s under Reilly. Yes, McNamara has made some mistakes both on and off the field in our opinions but it is plain to see that England have improved dramatically under him. Yes we may not have beaten the Aussies but we have a improved immeasurably. That is down to McNamara. Letting him go would be a poor decision as no doubt the next coach will be part-time, which will underdo much of the excellent work that has been achieved during the McNamara era.
I think you indirectly hit the point, but give McNamara too much emphasis. Some improvement to the England set up has clearly resulted from having a full time coach, rather than part timers in the past. However don't kid yourself that the team are now somehow better on the back of two defeats and being the third best side. We were actually beating the Aussies on occasion not too long ago and beating NZ more often than not. We've also made finals in the not too distant past on home soil - for some reason we are lauding a semi final loss over a humiliation as runners up, whereas the semi final loss may have just spared us the same fate. It's a sad state of affairs when the situation that England are in is perceived as a successful tenure for the coach. We are the third best nation and we were knocked out by a side who were massively outclassed in the final and we lost to Australia at their most rusty. I get the feel good factor of the WC has put rose tinted spectacles on everything, but there is a need to be objective.
Don't get me wrong, McNamara wasn't awful, but neither did his coaching abilities shine. He was probably better than expected, but only because expectations were so low to start with.