Of all your A tier civs Rome would probably be my first choice for demotion. They have a "jack of all trades, master of none," quality to them. You can have a solid game on any map, regardless of the VC you pick, but they won't be in the conversation when it comes to fastest win times because none of their bonuses are OP.
Scythia would be my second choice. Light cav have lost a lot of their shine as players have honed better strategies. Sure, they are good at conquest, but so is everyone else in the A tier, so strength of the other bonuses (offering an opportunity to do something other than pedal to the metal conquest) are the difference maker, imo.