Personally I consider 'differentials' a bit unnecessary most of the time - for the majority of the season what you want to do is maximise your points output, which might mean picking the same players as rivals. So as you say towards the end of the season it might be more relevant but even then it carries a risk, I mean unless you are WAY behind simply ignoring top players to create a differential could backfire, because you might have made up the ground with natural differences anyway, and you end up shooting yourself in the foot.
One season, I did a 'reverse differential' by using my wildcard that I'd been saving for a DGW that never materialised to largely copy the team of the person in second place in our work league
This season is going OK for me apart from when I transferred in Bamford early in the week to avoid price changes, a long term injury was then announced so I had to transfer him straight back out the following week. Then a couple of weeks later his replacement (Lukuku) got injured as well.