This is the way most pools do it, and you're absolutely right that statistical averages work out to 500k/block (using doge for the rest of this example). However, the block reward for the block you're _actively_ mining for is known when you're mining it. It is based on the last known block hash.
I've never been more happy to be wrong about something. And it does not surprise me that you've implemented a more efficient profitability algorithm. You should likely do the smart thing now and edit out your response in order to maintain a slight edge over the other pools, and then I'll follow suit in my quote above.
I had not bothered to scratch below the surface of dogecoin because it may very well fall out of favor after block 100000. But I'm glad you did. And I take notice of the fact that in a world where all dedicated single coin mining pools give way to opportunistic multi-coin mining pools, coins like doge may never gain popularity, as everyone will simply stop mining when a low reward block is presented. Fortunately for those who are positioned to exploit such small edges, the real world is never that efficient, and someone else can slog through those less profitable blocks instead.
If there were more smart people in the world, I would give it a week before waffle reaches 10GH/s, but it will probably take closer to a month. Which is good, because you probably still have a lot more you would like to implement, and it's easier to get certain tasks accomplished when you're smaller and more nimble.