i would replace the velites with more archers or heavy Inf. They seem overly weak in melee, they run out of ammo quickly, and dont have the killrate of your auxies.

Besides, thats what legionaires are for. Set them to fire at will and they will chuck some pillum down on those screaming savages. Almost any unit you can name is better than velites. Alright... They can be good set up right behind the legionaires, becuz the angle they lob spears is high, so fewer FF than archers, but overall, they are weak.

When your men finally make contact with the enemy, take archers off Fire at will and target them on the rear of the enemy. Wont stop FF, but should help some.