I see in cleric + BL a pretty well rounded combo.
The BL does a very decent amount of damage, hastes himself, slows. The cleric heals, and can deal a decent amount of damage at higher level. It also allows you to have two manageable characters if you want to raid later.
On that note, ranger is a rather box-unfriendly class, as your good dps is directly related to how often you can press on a button to fire an arrow. If you plan on healing on the other box, your DPS will suffer greatly. If you plan to always melee, you'd better chose a monk.
BL + Druid would work as well.