Exactly the same problem last night.
I play from South Korea on the NA servers, so lag is a regular problem to me. I've had tons of experience playing in 150-300 ping games so I definitely know what I'm up against.
I took a couple months off after the season ended, and when I came back there had been quite a few patches. I jumped in an ARAM for fun and my ping was 228(average for my place).
But this was NOT my normal play situation. It felt like I was playing through molasses. Tons of game freezes. Game wouldn't respond to hotkeys I pressed so I constantly wasn't throwing out skills. I would get 2 second hiccups on occasion when action was thick.
This is NOT a lag problem for me. The game was eerily smooth. It felt like a performance issue, but nothing has changed on my machine other than the new patch. I think people mentioning packet loss must be correct, and since I'm from a foreign ISP, this has got to be a server issue. Glad to see it's not just me and hopefully it's fixed soon!