Actually... with the introduction of a beastmaster ranger and a third model on the gameboard (the ranger's animal companion), you might not need to have another companion character NPC after all. In fact, with a little house rule tweaking you could use the animal companion as the de facto healer for the party.
Just give the animal companion the warlord's Inspiring Word encounter power (and rename it Inspiring Growl or something) and let the companion spend a minor action to activate it. Or use the shaman's Healing Spirit power instead, and use the animal companion in place of the spirit companion. In any event... three "PCs" on the game map make for a much easier time.