I honestly don't think the AEC is that bad (aside from setting you back teching wise). I don't see a Luchs ever beating an AEC unless the Brit player seriously micro fails. AEC costs less fuel too as of the V2 Mod so I'm not quite sure what the issue is.
Its not that luchs will beat AEC, it might but that would need some good flanking. The problem is rather that AEC not only deals no damage to infantry but also has problems to not miss against a light vehicles. That means it isn't good at anything. It is not good against infantry as it cant hit them and has no crush. It is not good against light vehicles as it struggles to hit them and is very easy to kill by anything supporting and it is not good against tanks as it has low penetration. It is the definition of useless unit.