My best value tickets to get to Manchester keep getting withdrawn, the latest one was actually withdrawn because a forum member saw another forum member with a Season ticket, and reported the anomaly.
It is the mission of some people to eradicate anomalies where possible, and that nearly always means putting prices up, not down! I don't criticise anyone for doing their job conscientiously, but I do not want to make the job of increasing our fares easier by listing anomalies in this thread
There are plenty of anomalies around, and plenty of ways of saving money on fares which aren't anomalies.
The first is split ticketing. This is fair game, I often recommend them to friends, and will sometimes go against the instructions from my superiors in recommending it in a professional capacity too. Split ticketing is fair game in my book, as long as people using the splits understand the restrictions which may be placed upon them by doing so, then there is no problem. These ways of saving money arise, as stated above, by different operators setting the fares for different journeys, and each operator having different policies.
The second way of saving money is created by starting or stopping short along the same line of route. Again, as long as any relevant restrictions are observed and the ability to start or stop short is allowed on the ticket being used, then these are fair game too. Again, these tend to arise due to different operators having different pricing policies over the same routes meaning fares change over time, or different ticket types with different restrictions are applicable.
Thirdly there are routing issues. These are where the only real anomalies lie in my view. There are two types of money saving routeing issues.
Firstly there are journeys where the cheaper fare is valid via a perfectly reasonable route which is relevant and sensible to the journey being made. I know of many of these too, and have suggested some to friends to use. I find it very hard to argue in support of getting these removed because the route is normally a perfectly reasonable, sensible, logical, practical, and indeed sometimes the only way, of doing the journey, but just happens to be cheaper than a fare for only part of the journey along the same route.
Secondly there are the only real anomalies as far as I am concerned, and these are routeing issues which allow tickets for journeys to be used on - quite frankly - ludicrous, illogical, unreasonable, highly circuitous routes which no one could even begin to argue as being sensible or reasonable for the journey on the ticket.
I am afraid the ticket you refer to fell into that category.
I have no objection to anybody using perfectly fair (in my view) and legal (i.e. conforms with NRCOC) methods of saving money, and whilst some would argue that using such completely bizarre routeings may be fair, I don't share that view I am afraid. Some are so completely bizarre that they are taking the p*ss a bit too much.
I know people will argue that nasty, greedy, money grabbing TOCs are the work of the devil, and how all possible methods should be used to save money, and if fares weren't so high in the first place it wouldn't be a problem (and I agree that many fares are too high, especially for certain TOCs or at peak times), but that doesn't necessarily mean that I agree with using some of the more obscure or unreasonable routeings.
I hope that makes sense.
Going back to the OP, no, I don't think anomalies as you mention are caused by historical mileage based fares, but more that over time different flows are priced by different TOCs, and even if they are priced by the same TOC sometimes some fares get overlooked at fare setting time if they are little used, and the busiest flows leap to the top of the screen when it comes to which ones shall get increased first. In the majority of cases TOCs have to keep all the fare changes within a very tight % to comply with the fare rise rules, so I am certain some little used flows get forgotten about.
