While it's true some guilds are better at numbers than mechanics, protectors really isn't just about numbers. If you mess up one interrupt in P3 you will wipe. If you mess up a lot of interrupts in P2 you will probably wipe as well. If you mess up interrupts towards the end of P1 you will put yourself in a very bad position.
Lightning storm is a one shot mechanic, bad dispels with the touch in P1 will also probably cause a kill. Failure to manage debuffs from the adds (keeping them up but not exceeding) can also cause wipes as well.
While a lot of the difficulty of protectors is in the numbers, it's simply just not numbers. If your guild sucks at interrupting you will wipe constantly.