Casters getting underestimated

I feel like with Territory Creation and Item Creation as abilities, Casters should either be every other servants priority target early on, or a desired alliance in a HGW.

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Like I play a lot of MOBAs and when the Carry's have had time to resource farm its basically GG. I know its technically the most mana-intensive servant for a master to have unless there is sufficient ambiant Mana in a given area, but when one servant can just stockpile nukes while the others are burning resources shouldnt they be more of a threat?