Gear
Tl;dr - 5 Necropotence, 2 Illambris, 4 Moondancer, 1 maelstrom stave on the back bar and 1 moondancer on the front

Necropotence is the bread and butter of this set. It gives SO much magicka, boosting your dps tremendously. You'll want the big pieces (chest legs) infused to boost magicka even further and the rest in divines. Illambris is another great set, but mainly in stationary fights. If you're running with a tank that knows what they're doing this is second to none, otherwise something like Grothdarr would work better. You want the head in heavy infused, the shoulders in medium divines. Moondancer will be your jewelry and front staff, and it is the hardest set to get since it comes from Maw of Lorkhaj. So, you could switch it out with something easier like Infallible Aether, or, even easier, Willpower, though at this point your front stave will not be a set piece or will be another maelstrom lightning staff. The reason you want Moondancer over Infall is I value the magicka over the crit since you'll be at over 50% anyway, and with most of our points not in boosting crit damage it is less helpful overall. All magicka enchants (you'll be at around 18k health with max cp and the pet active), spell damage on jewelry (with a good healer you'll be supplied plenty of magicka), leave the maelstrom enchant alone, spell power buff on the moondancer staff. If your healer isn't running blockade of storms, switch the flame staff for a lightning.

Rotation
Pretty simple stuff, but it packs a serious punch. We prioritize the skills in terms of duration and synergizing with each others' duration. You will be light attacking between each skill except for volatile familiar, which you will block cancel, elemental blockade, which you will bar swap cancel, and the final force pulse or crystal frag, which you will also bar swap cancel. Have constant uptime of spell power pots (spell power, spell crit, magicka return).

Liquid lightning, volatile familiar, blockade, daedric prey, force pulse 5 times, on proc of cyrstal frag replace one of those force pulses with it (so if you have 2 procs you will only have used force pulse 3 times). When the enemy is below 20% health, after daedric prey bar swap back and spam mage's wrath. When your ult is ready, use elemental rage unless it's purely a single target fight and the boss won't move at all. That's it. Seriously. It's super simple.

Sidebar Skill Notes
I prefer bound aegis over inner light because it gives 1% more max magicka, boosts spell power by 2%, gives us that extra little bit of armor that has saved my life and thus prevented a wipe before, and the crit from inner light is given by the pots I use. But, if you prefer the regen or aren't using pots, you can swap aegis out for inner light on your front bar and put hardened ward on the back bar. It'll give you quite a bit more survivabilty, and in groups with a poor healer and/or tank I sometimes do this.

Champion Point Notes
We have a bunch of points into thaumaturge for the passive that boosts damage by 10% when the enemy is off-balance, and with a good healer or when running dual lightning staves that's a lot (constant).

Soloing
For when I'm alone, I take off aegis for Hardened Ward on both bars so that I have that huge armor boost for me and my pet. I take off daedric prey and put on Elemental Drain for the boost in sustainability. I take off Mage's Wrath and put on Power Surge for the constant uptime of major sorcerery without the use of pots and the constant heal. I switch my spell power pots for spell crit, health and magicka return. I take off Ice Comet and put on Energy Overload for the availability of a third bar for escaping and magicka regen. The the third bar is Dark Conversion, Hardened Ward, Volatile Familiar, Ball of Lightning, and Restraining Prison. A few dark conversions will get your magicka back up to full, and ball of lightning with restraining prison will let you get away if you need it, and an added bonus to prison is it heals you. Familiar is on the bar mainly so that when you switch to the bar it doesn't die.