I cannot speak for Unity or Dirt rally, but I can tell you that the rest run on max settings without a hitch.
You cannot just make assumptions about the OP and giving an answer on this assumption. When you say overclocking has its place, then yes of course it does. Saying like you did previously where Overclocking is beneficial no matter the GPU is not correct.
If we start making assumptions we can say.. What if the OP runs a core 2 due processor and wants to overclock his GPU for better performance.
To be able to answer correctly, we need to understand why this person needs to overclock. Perhaps your assumptions is right, perhaps it is wrong. lets not make assumptions and get answers first.