^ Nailed it. 

When it comes to an arena/PvP elimination RP like a Holy Grail War, the biggest factor is the players and how willing they are to work with you and the other players to make sure things go well. This goes without saying in every RP, but more so in this case. I personally think that in an RP Holy Grail War, which is an open and collaborative environment, you've kind of got to take the 'absolutes' present within the Nasuverse with a grain of salt, otherwise you could just potentially Gae Bolg everyone to death. If they're all making their own servants, then make it a rule that things like Barbed Spear that Pierces with Death are not allowed in the same capacity of which they are presented in F/SN to ensure that other Servants might actually have a chance. 

This shouldn't always be the case, anyway. The Fifth War was weird and has a bunch of exceptional servants. 

On a somewhat related note to that; dogdang not every Berserker needs to be an unstoppable murderhouse like Herakles.