Switching between servers forces a redownload of the entire patch

I'm playing on both OCE and NA servers, I recently patched OCE to preseason, played a game, then went back to NA. There was a 1.5gb download waiting for me pre-login screen, followed by a 3gb patch on the play button. I played one game on NA, and went back to OCE thinking it was all done, and faced a small 1.3mb download which wasn't a problem. However, upon clicking launch, I am once again faced with a 3gb patch on the play button. Is this going to be permanent? Coz I really don't want to have to wait 2 hours every time I want to play a game on the other server.