I don’t think TKs are in a bad spot. They have a strong role in protecting siege, particularly Siege Onagers, and unlikely halberdiers, can do so against cavalry and infantry at the same time. They dumpster almost every melee unit except a few unique units like Cataphract, Samurai, Jaguar Warrior and Leitis, and they have access Bombards and SOs with Siege Engineers to offset the weak archery range to try to make enemies attack siege directly in most cases. At most maybe +1 PA or .05 additional speed but I would lean against this until we have a better idea how strong melee focused civs are with the updates to pathfinding.
The key to using them is to make your opponent come to you. See video below where this is shown against Mayans no less.