In your simulation, I suggest you don't use any of those formulas, and just model mining as though it really is at the base level. Randomly generate a number between 1 and 100000, and if it's below 1000, it's a share. If it's below 10, it's a block.
I thought about doing this. The problem is then I need to process the workers in a parallell fashion. Meaning run multiple threads/processes. This is because now both miners are racing each other. This complicates the code significantly, but also now you have introduced variables that you didn't have before, race conditions within the operating system.
I agree that would be a more accurate method, but to do it really properly you almost be better off just setting up a real pool and have real miners mine shares at different rates and take stats.
Minus my admittedly inefficient block/share time random generation (working on that), as long as you trust the probability it should be accurate, to the best of my knowledge. The block solve for each block is used by both workers on that block, so they can accurately be evaluated serially.
Edit: also, 2 workers is a really small sample in terms of solving a block, something that is in reality really consistent