To be fair to SWR, if you accept the necessity of cutting 2tph from the main suburbans there's not much choice if you want to give everyone a useable service. Their solution gives at least 2tph everywhere except Leatherhead-Effingham. More than that care has clearly been taken to spread the services quite evenly as well - half hourly from Epsom, every 15 from Motspur. Whilst obviously not ideal I don't think there is a better solution for achieving this than what they're running.Presumably SWR dont care about demand and want to dump all the Epsom to Dorking passengers onto GTR (which have a full service bar the Guildford to London Bridge peak extras and some early morning trains before 6:30) because it is an easy way to reduce services without leaving anywhere with no service, and believe Epsom to Raynes Park wont require more than 2tph (which is ridiculous given it has 6tph in the peaks usually).
And that's before noting that they're running 3tph from Epsom in the morning peaks which is a service level pretty much on par with the Woking suburbans (the only other group with peak extras) which under normal circumastances possibly even load better than the Epsoms, and is a line which doesn't have the luxury of the choice of extra services from Southern