Celtic Heroes

Rogue/Druid combination best imo, rogues are the next best thing to tanks and if they use fast reflexes while the druid is using howling wind the chances to get hit are minimal. Bless will also lower chances to get hit by skill attacks used by the mobs, and rogues will still be able to do good dmg while staying alive.

I don't have a rogue to dual box with, I only have a ranger. But I can say that my favorite combo for leveling is druid/rogue. Kills are faster and survivability is best than any other class. When I level my druid I try to get a rogue to group with.

Rogue warrior is an awesome combo if war has enough sigs

For leveling if your rogue has a good solo build a rogue and lure/dps mage would be a deadly xp combo. Its what I used to do leveling to 190 but my mage was too low to dps.