Nope, not essential at all. Still, IMO you should balance out your stack to make it androgenic enough for your body to keep up normal (higher than normal is also accepted by most) sexual functions. So depends what you are running.
I agree with others that Anavar/Proviron is too mild stack to waste your time and health on. You need a base for your cycle, personally I would go with NPP, Masteron (or Primo), and throw Var which ever you see more fit as kicker or finisher. Proviron I would run throughout, if possible.
Then again, I do personally prefer also a HRT dose of Test, but I'm on it year around, and it would be very inconvenient for me to stop it while blasting other compounds... So adding small dose of Test to any cycle certainly doesn't hurt, but is by no means a must or "the building block of all cycles", that's broscience/interweb-mythology...