UNIT - Creature Balance + Visual Changes

What definitely needs to be done with the nimble riders is to increase their maximum damage to the level of their counterparts. And also give them some kind of immunity to curses (like the Megeras), or reduce the damage range, or something else along those lines. Then it will definitely be a tough choice before deciding which upgrade to choose.
Replacing the Titans' lightning bolt attack with a regular attack is a good idea. In my opinion, it would be worth limiting the number of casts (if possible) and making the Titans flying creatures. The teleport animation can be borrowed from the Trolls.