I have a few ideas for a companion character. Basically, a dm or party controlled npc with some, but not all, the powers of a normal class.
First option is the House Seleucos Riven speaking in the rp thread. Another option is to have the party come across a summon who for some reason, helps the party fight. Choosing summon basically means you get something that fights and doesn't say a thing. Or you can keep things as is and escape with four people. The choice here will be temporary, lasting only for the temple escape so you don't have to worry about anything long term.
Regardless of what you choose as a Companion character, class also needs to be decided. It seems striker is pretty clear, but what class? Anyone have a preference?
Might be slick to have a rogue in the group, with one of my at-wills granting invis - we'd be assured of serious damage. A good partner to my built is a striker that isn't afraid to get into melee. With a nasty ranged combo of warlord/assassin and wizard, and our Monk, we just need another melee striker so my mark gets triggered more frequently OR the enemies suffer the wrath of the monk and other melee. We need to make the enemy need to pick their poison - and Joshua is a BAD man to not focus on. So, they either attack him OR the other melee and suffer my mark, or they attack me and ignore the two melee monstrosities chipping away at their backs. Pretty good combination.
Otherwise, Josh and I just need to coordinate our melee movements a bit better so they need to attack him and suffer, or attack me (to little effect) and suffer. Ruby's player excelled in putting her in situations where she mowed people down on the regular. Josh and I just need to get a bit more experience fighting together and we'll be there as well.
In addition to my earlier thoughts (above) - With Josh and I threatening multiple parties with AoO - and Masoom and Verity assaulting at a range (and healing through V) we have a very dangerous party. Masoom's ability to damage, teleport and control enemies is bar-none some of the best 4E controlling I've ever seen. He sets the party up for success then makes the enemies pay for moving, for not moving, etc. With Verity's shadow shrouds, healing, offering basic attacks, she effectively acts as a striker/leader/controller as well.
This is a very well rounded group - we just need to make sure we position ourselves well to maximize our combat abilities, flanking, area-attacks, etc.