Having recently done this for my Shaman, I'll throw in my 2 cents.
The first hurdle you will run into is getting all the toons flagged to do the Naggy/Vox raid from OMM.
Sic shows this in his vid and even recommends doing Tower of Discord. I agree with this completely.
You need to kill 7 raid bosses. The nice thing about the tower of discord is it has a normal and hard version with separate lockout timers. So you can do some from normal and do the same ones from the hard version if you want.
I actually started out trying to do crystalos but it requires a key and the key requires a drop from the Meldrath raid and the Meldrath raid zone also requires a key. So in order to do crystalos you have to do two ridiculous lengthy old raid key quests.
Once you are flagged then you will have access to do the vox/naggy raids from OMM.
I was able to do these using the macro Nookiecookie listed above. I did it with 6 toons. The macro will make everyone mages unless you specify one toon by name to be a necro. I highly recommend using at least 1 necro. I would then pause the macro to do splits so my mages would not auto-attack mobs while I was splitting them with the necro.
The Naggy raid has the following issues:
If you die and come back in you start at the beginning of the zone and have to deal with either killing your way back down or trying to invis yourself back down.
Splitting Naggy and Roykl takes timing and luck as you'll see in Sic's video.
The Vox riad has these issues:
Although you start right at the beginning of the ice giant area. There are some spawns that repop the diplomat, three tentacle terrors, and a blizzard spider. Two terrors pop outside vox's lair and one inside vox's lair.
The other issue is the tentacle terrors have a knockback and there are hidden pits that they can knock you into that are yellow areas on the map. If you fall in you will be attacked by polar bears and more terrors and these can possibly path back up to your group when you die.
The other final issue is there are a bunch of priest ice giants that heal and basically you have to fight through their heals until they run out of mana.
After dealing with these issues you then still have to deal with splitting stuff from vox's lair. The nice thing about this is she will reset if she tries to come outside her lair at the rock. This makes her easier to split from the trash if you can deal with the healing priests.
Once vox is by herself wait for the trash repops kill them then engage her.
Hopefully, you can time it and position your pets so that she is behind the wall but they can still hit her this way they avoid her fear.
You get 2 brews for each of the raids.
Personally, I just did them once to open up the items on OMM and then used Overseer to farm tetra to buy brews from the Overseer merchant in PoK. Each brew cost 1900 Overseer Tetra, Using the Overseer Lua on multiple toons and then trading the tetra to my Shaman I was able to get them all in a few days, I'm on FV so I don't know if you trade Tetra on other servers between toons.
Anyway hopes this helps.