I have recently started playing again boxing a Barbarian Shaman and Barbarian Warrior and would like to add a third. I am considering all the other Barbarian Classes. I am also considering a Mage I have never played any of the above.
bard or zerker. bard gives you more survivability and utility, zerker gives you more raw damage. My preference would be bard. Barbarians can be berserkers though!
zerker (DPS) or bard (run speed +adps) once you have your core set you can always level up or heroic some buff bots , and then level them up later to allow for campfire in to buff your group
Bard is the obvious choice. Good buffs with no effort, tracking and pulling, even some okay CC. Doesn't need to much except auto attack and even that won't make or break you. But really when you already have a SK and a Shaman it doesn't really matter the third, since you've basically got everything covered already.
Bard for ease of use Zerker for pure dps Best option is to make a bard (fourth), park it with melody so super easy, and add zerker to play as the third I promise you will NOT be disappointed.
Zerk (rogue for certain races) would probably be best DPS. Bard is good balance of DPS and utility. Depending on how long you box, the late game some named mobs will be melee immune so a wiz/dru/mag/enc/hybrid are viable considerations, but that is a non-issue except in a few rare instances.
Thanks everyone for your suggestions. In the end I decided what I really needed was a puller, since the shaman needs to med, and setting the warrior as main tank seemed to cause the Merc healer to follow him. So I made a Zerker. The class description said something to the effect that they shun armor and love to die. As far as I can tell all of that is true! My Zerker is now lvl 8 and only has the armor obtainable by quests, and as an example of loving to die, after killing the spider queen he was limping back to camp (well outside her cave) when she came running out of the cave and killed him. I know that fastest way to lvl up is to use the war Merc but I am more interested in learning the class, and playing in a more classic way. Another concern I have is can the Zerker pull (split mobs) at higher level? Anyway I made a monk to help the Zerker with the harder quests and figured I could always lvl up the monk if the Zerker proves unable to pull at higher levels. By the way I am loving the axes.
You should consider replacing the ZER with MNK or BRD. You will continue to struggle with pulling. The best way to play WAR/ZER is going to be to have the WAR tank multiples, or to let a tank merc off tank. If you want to split, you need to replace a toon, probably the ZER.
You need DPS. Warriors are meat shields, not DPS. SHM can sort of be DPS with their DoTs but not as much as a true DPS class. Personally I'd go with a monk. They can pull for you, their DPS can be high if properly geared, and most importantly they can DROP agro when needed. My other choice would be a Wizard, but the problem there is that if they over-nuke they're going to get agro, and they can't drop it; the warrior will have to out agro them.