[quote=@Lonewolf685]
The horrifying moment you realize you have a Caster and everyone else has Magic Resistance. 
Whelp, I always did love a challenge, thought I find myself for more empathetic to the plight of Medea. No wonder she had to drain all those civilians.
[/quote]

Only Saber and Rider have any significant resistance so far, and that shouldn't be that much of a problem to someone such as Tamamo. That said, the Servants so far indicate that this will be HGW with little attrition between he Servants. No one seems to have that bad of a personality and there's even the possibility that they would get along (Saber and Caster in particular) were they not meant to kill each other.