I get the same problem. Mine can take several minutes, possibly up to 10+ minutes before the Magsafe 2 starts to charge. And I also get the impression, the more its charged, the shorter the delay in waiting for the green charge light. Which is a real problem when you are working away and you see the battery about to die, but on connecting the magsafe2, nothing!
I have a work around. If you can get hold of an 85W Magsafe 1, plus the Magsafe 1 to 2 adapter, the charger 'always' works instantly.
I have a retina, MacbookPro 15inch, core i7, SD ram. MacOS X 10.9.2.
Mine MacbookPro 13" (mid-2014) has the same issue.
When plug in power adapter, charging process starts in about 30 seconds.
During the charging process you can unplug and plug it back and it starts charging instantly.
It seems, the time, that it takes to start charging depends on how flat battery is?
Is it technical fault? Or it's behaviour of "MagSafe2"?