I recently bought an ESP EC-256, and so far I love it, but I would still like to get some better pickups as the sound on these is a little muddier than I like. I play a lot of metal, and I want to get some Dimarzio D'activators and put some 6X6 pickup covers on them, but I heard that to put those types of covers on a pickup, you should pot the pickup first. So are the D'activators already potted? And if not, would it be a good idea to pot them?

All Dimarzio pickups, and almost every other quality pickup, are potted.

There are a few exceptions, but they are for a very niche market (Vintage).
“Ignorance more frequently begets confidence than does knowledge.”
Charles Darwin
Quote by dthmtl3
What are "potted" pickups?

Potting in general electronics terms means that a circuit of some form is sealed by being coated with a material such as epoxy typically for the purposes of durability and/or waterproofing.

In guitar pickups, it's used to prevent the coils of wire inside the pickup from vibrating, which causes microphonic feedback. Usually pickups are potted with wax, but sometimes epoxy is used.
Quote by Axelfox