I suggested on here it before and got shot down for it!
Realistically Clacton doesn't need more than two units per hour. The town isn't nearly as big as some people seem to think - at 53,000 it's only 25% bigger than Braintree, for instance - and isn't exactly first choice among the local seaside resorts. If this means a second service per hour, extend the Colchester Town terminator and make it call at all stations east of there. The Walton train could then become a shuttle as per Sundays, possibly with an improved frequency if the timings work well (very marginal). Otherwise however, one 8-car 360 should suffice.
As for the Southend comparison, this is completely unfair. Clacton is on a branch that sees 2tph; Southend Victoria is on a branch that sees 3tph. Even before Southend itself is considered, the latter is far busier: Billericay, Wickford, Rayleigh, Hockley and Rochford combined have a population of somewhere in the region of 125,000; throw in an airport, the need to facilitate links to another branch line, the local station for both Southend Hospital and Southend United F.C. (as well as a fair proportion of the north of Southend), and of course Victoria itself, and you have a line that if anything needs 4tph.
On the other hand, the entire Tendring district - which covers all stations in Essex beyond the Colchester urban area except for Wivenhoe - has a population of only 140,000. With this in mind, this area does very well in railway terms; it has three branch line termini, three direct services to London per hour (two of which can be considered InterCity), electrification throughout and even the odd service which in years long gone would have run through to Liverpool!