How is Caster still around? One of the big problems with Team Caster in Fate/Stay was that she was lethally draining mana from the surrounding townspeople to fuel her and Assassin's needs (both for combat and day-to-day functionality). Now that she's not doing that, where on earth is she getting the mana?
I assume her case is similar to that of Saber in the Fate route. Presumably, she's already got a sizeable amount of mana stored in her body and keeps the levels by eating, sleeping or just some old fashioned "mana transfering" with her master.
Also, the main reason for her mana-draining was so she could become powerful enough to fight the other Servants. If she doesn't need to blast people every other day, she doesn't need nearly as much mana.