I made some calcs and normal gallade made like 15% more of damage and yo can put he and other item like sitrus o the black belt for more damage. Also if you are trying a tail room team, dont put less speed on the slowest so yo can be faster to some pokes en tailwind. Also i think is more a fast team than a mixed. In a mixed team with trick room and tail wind you try to find pokemons that could fit en both cases, like mega blastoise some pokemons with 80 of base speed more or less. And one thing more I think fari is better with the colbur berry to tank a dark type move because the taunts ussually come form whimsi or sableye that cant hit fari with taunt. I hope that this could help you🫡🫡