For each punch to have its own crit/direct hit checks, it would have to stop being a single attack in the server code. Nothing else in FFXIV works that way, I am not sure if it would even support doing that without also making it into having to press an action three times. I think it would be far easier to just change things in how it is displayed. If you absolutely do not want to just have three times the same number, you could just introduce RNG to split the total damage in different ways across the numbers displayed for first, second, and third strike, while always having them add up to the single damage number the server returned. That way the client can handle it, and you should not put extra workload on the server side just for what amounts to a display effect cosmetic, right?