I suppose this is natural when one of the main sub-plots in this story is the introduction of Turlough, which means that we're back to having three companions clogging up the TARDIS again, which is too many. This problem is made worse when one of them has a large back story to deal with. In fact Turlough's deal with the Black Guardian is going to make him a difficult companion to write for full stop. After all if his raison d'etre is to kill the Doctor how do you prevent him doing so if he's permanently with the Doctor.
Anyway the question will be is TARDIS big enough for four?
Whilst the story is a rather gentle one it is quite a good one. There's food for thought, a new interesting companion, the Brigadier's return - twice & it is nice for the enemy to be fighting for something so 'ordinary' as the right to die.