That's not really true..by the time they build the new superior defensive unit, you are present with your attacking force. They of course have to be expecting the attack the moment you start building one so they can research the new one and build it themselves, otherwise they will be too late. Essentially, it takes them just as long to stop an attack as it takes you to start one (minus some inherent defensive bonuses), except the travel distance, which with 2-5 speed units is less than it used to be. All in all, attacking is more dangerous all around (no emergency whip / draft / units are very expensive to mass buy), especially combined with hilarious insta-heal promotion. With fewer and thus more valuable units, insta-heal is like e.g. 5 free Civ 4 units. One replenished companion cavalry is like 37 more cities crushed (not an exaggeration ). In terms of the OP, the units are more valuable because there are less resources to make them. You don't have stacks of doom because aside from them being illegal, you can't afford > 1 unit. That doesn't prove they are too low, it proves that people will not use 50 companion cavalry simultaneously (thank god).