Liko with the help of Rosskag goes over Magicka Necromancer PvE DPS'ing in the video below. Make sure to support Liko at his Patreon! And check out his website, Liko.gg, a friend of the ESO University website!
Key to the rotation is casting Blastbones (BB) as often as possible. Ideally, this will be 1-in-3 skills, but sometimes it can be 1-in-4 or more, so you'll have to prepare for that.
In between, keep your DOTs refreshed. Unstable Wall as the most important followed by Orb, Boneyard, Skeletal Mage, Siphon, Barbed Trap would be a rough order of priority. When nothing else needs casting, use the spammable.
When you use Medusa set, you should replace Barbed Trap/Channeled Acceleration with some other passive/active skill (e.g. Expunge), because Medusa gives you Minor Force passive
- BlastBones (BB) - Skeletal Mage - Barbed Trap
- BB - Boneyard - Unstable Wall - Siphon
- BB - Orb - Spammable
- BB - Spammable - Skeletal Mage/Barbed Trap (alternate)
During execute phase rotation remains unchanged
Spammable = Skull / Force Pulse etc