Linking Sets is awful. You need to be able to select a whole set of pupils and COPY them into other subject sets. As soon as you have a class that is not in line with "forms" then there is not a simple way to just copy them over. For example, PE will be 3 Subject Sets worth of pupils, not 3 "forms", so you have to go a terribly long way round to get the pupils in.
Would definitely be helpful to have a template set that you can then refer to and copy pupils from this set to another. Linking sets is almost too easy and if you get it wrong it will daisy-chain and mess up all set membership in one fell swoop. Linking sets is good but too easy to make a mistake and time-consuming to revert.