In Vanilla, I have always found Thrace to be a tough opponent.

Those *&^(*^ Bastarnae race across the whole map at double time and arrive at my lines only "winded!" And the Falx aren't noticeably slower.

His cavalry gets hammered, but cuts into my cavalry a bit before breaking.
My archers fire at the falx and Bast, my spears and swords take the hit and my cavalry slashes in from the flanks. Some tough fighting, but then they break away.

THEN his malfing pikes show up with archers shooting along with. My cavalry is already down 60% in numbers and tired, many of my arrows are gone, and slices have been taken off of every unit in the line.

Yes its beatable, but if there is a faction out there that can fight without cavalry its Thrace.