A single +29 speed mods can not decides outcome of a battle in high level arena: Evasion lead, pre- and auto-taunter, Rex and Han Solo are possible solution to overcome bad luck in mod lottery.
However, 4 set with 50 speed points difference between you and your opponent can make a difference. And you can't get this prize as a purebred one shot lottery as the probability is too small. Resources spent on mod farming is the deciding factor as the variance is also really small
From a player who probably spent more than 40k crystals worth into mods (crystals from arena rewards).