I don't think rerolling is really "rerolling" exactly

In the announcement they say, "your Rerolls aren’t affected by the other players’ Rerolls (so you don’t have to try to game the timing of your Rerolls)." I couldn't figure out how this is possible at first. If someone else rerolls into the #1 S-tier hero before I click my reroll button, that hero would be removed from the hero pool and I can't get it. So how can they make this claim?

I think the way it works is at the start of the game each player is randomly assigned 8 heroes from the hero pool, four of them shown and four of them hidden. When you "re-roll" you're just switching out to one of your four assigned hidden heroes. There are plenty of heroes in the hero pool to assign 8 to each player in advance.

This doesn't really change anything, but in case anyone was thinking they will have to be fast with their reroll buttons, I think this is why it doesn't matter.