Even without Shaak Ti, with 3 501st clones you get +12% bonus speed. I am too lazy so I'll just round it down to 10%. Assuming your Rex is at 300 speed(for reference Rex's base speed is 160 vs BSF's 156, so getting at least 300 isn't that impressive) with 10% bonus speed you are looking at 330 speed at the beginning of the battle. The majority of top 10 players in each shard should have no problem in getting him around 310 speed which will easily make him go before most of the DRevans. So Shaak Ti is mostly there for the other bonuses, not the speed(though the bonus speed still helps).
