This is one of those cards which initially looks poor, but is subtle and better than you think. 2 cost for 1 is pretty poor in , and its other stats aren't anything to write home about. However, it's the ability where this card shines, given the right situation.
Once you have the ability activated, there are two situations which make the sailor a good choice. The first, common case are the many when revealed effects which damage characters who are exhausted or committed to the quest. The sailor just laughs these off. The second (and more awesome) case is when you can use a readying effect to have the sailor defend against an enemy that attacks during the quest phase. These are more common than you might think, and can really throw a wrench in your planning. The sailor helps with these situations and means you don't lose an ally in the process. Honestly, there are few things more hilarious than a puny elf shrugging off an attack from the Balrog without getting a scratch.
These things are situational, of course. There will be plenty of times where an Ethir Swordsman is going to be a better deal, but in those times when the sailor's ability comes off, he's well worth it.