Technically, the first mission is the corsair mission, since it counts towards the protector title, but I can get to the diggings one in a matter of hours.
Also, you accepted the reward for that one where you go test the new sword with the guy? If you abandon it once you get 10 kills you can keep getting it over and over, and have him kill higher level monsters, and if he's in a mob, regardless of how many he's killed, he kill the rest. That paired with the bounty and the scroll of +50% exp, you get massive amounts of EXP. Faaaaaaaaaaaaaaaaaaast leveling.
All you need to do is attack the enemy he's attacking once, so you can get the exp, and since he's an ally, he doesn't get any exp from the kill.