I think the DLC was worth it, considering that it was only 400MSpts (when usually DLC like this would be 800) and that you get the 2 extra characters for the Mercenaries Reunion. Sure, that might not sound like much, but for 400MSpts, it's worth it!
It took me around 50 minutes to complete Desperate Escape with my brother on split screen, but there was 2 or 3 deaths involved, and we ended up killing over 200 enemies total.
DE is more about the action, whereas I think LiN is more about the story and tension (and to bring back old memories to RE1 fans). Sure, DE didn't give me the "OMG this is awesome!" feeling as soon as I began, but that's most likely because I wasn't playing as Jill & Chris in a rather familiar looking mansion (huge REmake fan here)
If people think either DLC is too short or too easy, I highly recommend playing on veteran / professional (especially professional). LiN was great fun on professional in co-op with a friend, not being able to see the enemy on the map during the sewer scene required good communication and teamwork. If you can't get someone to play co-op with for either DLC, don't bother playing until you can find someone. This game & DLC was made for co-op between 2 friends in my opinion.