I started Playthrough 2 at Level 36. I went to Jakobs Cove ('The Zombie Island of Dr. Ned' DLC) and found out that the enemies are at least level 42. I couldn't even get to the first objective without being eaten by zombies. I had to level up a bit to finish that DLC's first mission.
After I finished the main questline of 'The Zombie Island of Dr. Ned' at level 46, I then went to T-Bone Junction ('The Secret Armory of General Knoxx' DLC) only to be jumped by assassins that are level 51, in the first mission. They deal enough damage to deplete my shields and health in at most 2 melee hits.
Like this question for Borderlands 2, is there a recommended level for starting the Borderlands 1 DLCs? Will I encounter enemies that are too hard if I go early, or too easy if I go late? What about weapon proficiency? Are there also recommended weapon proficiency levels for the weapon types that I'm gonna use in the DLCs?
Best Answer
I don't know about Weapon Proficiencies but I am pretty sure they were never really that important.
According to this, Claptrap and Knoxx start at level 35 for PT1 which shows that they are post-game DLC. You technically should have done them in Playthrough 1 after you beat the main story then moved onto Playthrough 2 from there.
Because they are post game DLC's you are supposed to hold off on attempting them in Playthrough 2 until after you finish Playthrough 2/hit Level 50. They will always be 5 levels ahead of you until you hit level 50. Then they will scale with you from there.
Zombie Island and Underdome are both mid-game DLC and are probably low-mid 40's. But when you hit level 50 they will scale up with you as well.
So:
Weapon Proficienies are just a bonus. Not really important.