Does it count as a day 1 patch if you haven't slept since launch? (Note -- if I'm still causing fixes 'day 1 patches' next week, notify a medical professional)
So after beating my head against a wall about what needed to be optimized, re-jiggered, ripped out or reworked, it turned out that it was just a good old fashioned teeny tiny bug (fixed by changing 5 characters, actually) that was red-lining some users CPU's. More importantly, it's gone now! Two days of chatting with dozens of players revealed a pattern cued us in on checking the most unlikely and innocuous of places, leading to the fix.
I want to Thank everyone I chatted with and everyone who reported problems, you guys are lifesavers!
--Sean