This is the argument put forward by the large firms disatisfied with the LPC - relevancy... However, the LPC, as I see it, is part of the formative training in much the same way as the LLB/CPE is... you study elements that will quite possibly have nothing to do with the field of Law you end up working in... And further to that, as I understand it - the LPC is the "practical" element of legal training whereas the LLB/CPE is the "theory" element. It is simply a part of the process - albeit at a more "professional", formal level.
The key point with the LPC is you've taken that formal step to becoming a professional... you've crossed the line.
In terms of training you for your particular field of Law - I assumed that was the point of the TC... up until then you're being equipped for a career in Law in it's widest possible sense...
Again, from my point of view - I can only see this as good and right and proper... and sensible and prudent! I have a drinking pal (well, when I was what I'd call myself a drinker!) who worked for 20 odd years in Commercial Law for a multinational construction company - he was made redundant... didn't work for a few years - last year he got a job in a local, small town solicitors doing 3 days a week in Conveyancing... An extreme example, I appreciate that - but the point is, nothing is guaranteed to be forever.