Do i need an np5 zerkerlot for farming?

No.
at level 80 with a decent CE he will always do the damage needed to clear a wave of doors for QP or hands for embers.
Source: Me. I've got a NP1 berserksalot.

Try to get NP2 if you can. Getting a second copy gives the biggest increase in NP damage.

Source: I have a NP2 zerkalot :P

Not at all! Lancelot has gotten me through so many things since I got him early last year, farming or otherwise, and I didn't get him to NP2 until Merlin came around. All you need to do is level him up enough to smack things around, slap him with a Kaleidoscope or some other charge CE, and maybe a Waver for support, and let Lance smack things around