The two last rows at the very back of the stalls are officially classed as having a 'restricted view' when in fact they offer a pretty good view of the stage and offer good value for money, and while these rows are admittedly quite far from the stage there is very good legroom as an added bonus! The other section of the theatre that offer good value for tickets at the Old Vic is in the 'Lilian Baylis' circle where there is consistently bargains to be found.
Seats located centrally at the front of the stalls section from row E through to L probably have the best overall view of the stage along with rows A up to D in the dress circle. All tickets at the Old Vic in these sections will be priced at a premium but if it is a completely unobstructed view of the stage that you are after and finance is not a consideration then this is probably where you want to be.
As productions at the venue tend to be short and strictly limited seasons that often feature big name actors it is unusual to find any official discount tickets at the Old Vic. Producers of shows naturally want to maximise the profit for each production and if they feel that they can get away with selling all seats at face value then it is not in their interest to offer any reduction in the price to agencies, which why you will find that tickets bought online through third party websites for this venue often have a booking fee added to the price. Booking tickets directly from the box office at the theatre can be beneficial for productions at the Old Vic as they should be sold at face value only.
