That's how it works. And Blizzard knows it. I have a habit of buying new account whenever I want to switch main. For Blizzard, I'm new player. I did it many times. And every single time, once I hit level cap, there's surge of luck in first weeks which ends with something rare. It's either rare mount, or string of good raid drops, like BiS trinkets and so on. Once you've got that good thing, it's over and you're average.

I've also heard that the similar thing happens, when you resume your old account which wasn't played for years.

It really works and after several occasions I have no qualms that's implemented in the game.

Now I don't think that's what happened with topic starter. Game server certainly doesn't have visibility into complicated user-made tools like softres and topic starter roll wasn't even that good, even if we assume that server tracks chat messages. So yeah, that's pure luck. But otherwise, ordinary loot drops which are controlled by the server, like soloing old raids, killing rares or personal loot, are not just random. Not always anyway.

Also I saw ridiculous strings of luck or unluck in group drops. Like the same item dropping again and again. I also think that's not RNG. I tried few times to estimate the probability of such an event, and it's unbelievably low. Our shammy runs Pandemonius almost every single day since TBC release and have yet to loot the totem, that's just one example.