Why aren't the enemies scaling with my level in Borderlands 2? [duplicate]

In playthrough 1, outside of the DLC, there's no such thing as scaling. Enemy levels are determined solely by the area they're in and your mission (certain missions effectively "level up" areas, notably Sanctuary and The Dust). You can easily check the level of an area by checking out the vending machines in the area, they sell items scaled to the level.

DLC in playthrough 1 scales to your level...ish. It maxes out at level 30. I played the DLC as a level 34 character and was disappointed to see everything was at level 30 in playthrough 1. Not sure if it has a minimum level it scales to.

Playthrough 2 works the same way until you beat the Final Boss; then everything in that playthrough scales to your level (except mission rewards for missions picked up before the final boss).

Playthrough 3 works the same was as Playthrough 2 after the final boss: Everything scales to your level, period. In team play, it will always be scaled to the highest level player's level. And you have to be at least level 50 to unlock it, so enemies are effectively level 50-61 at all times. Though if you take a mission before leveling up, the mission will still stay at that lower level, as always.

Basically the game works like a standard RPG without level scaling until you A) beat the game twice (because you should be maxed out anyway) or B) enter a DLC (because you can do that at any time so a preset level would be a really bad idea)

To address OP's edited question, enemies do not actually "scale", or at least from what we know of. In PT 1.0, enemies do not scale, and are based in the areas where you can find them (in terms of storyline progression), and so is PT 2.0, where enemy levels are based on area. Only in Playthrough 2.5 will enemies "scale", to level 49 (bosses 52).

On average, most players finish PT1.0 around level 30-32, so when you start TVHM (PT2.0), the enemy will "scale" with you, starting at level 33. Ironically though, they do not actually scale in PT 2.0, instead, increasing in level until a cap of 52 in order of storyline missions. Here's an example:

This is the basic route they expect you to follow for most of the main storyline:

• Windshear Waste (Claptrap's Place) - Starts with enemies level 33
• Southern Shelf - Liar's Berg
• Three Horns - Divide
• Sanctuary
• Frostburn Canyon
• Three Horns - Valley
• The Dust
• Bloodshot Stronghold - Enemies here are around level 36
• Bloodshot Ramparts
• Tundra Express
• End of the Line
• The Fridge
• The Highlands - Extraction Plant - Enemies here are around level 42
• The Highlands Overlook
• Thousand Cuts
• Opportunity
• Wildlife Exploitation Preserve
• Control Core Angel
• Eridium Blight - Enemies here are around level 46
• Sawtooth Cauldron
• Arid Badlands - Boneyard
• Arid Badlands - Badlands
• Hero's Pass
• Vault of the Warrior - Ends with enemies level 52

Basically, based on the areas that Gearbox expects you progress through the storyline, the enemies will increase in level up to the warrior. This creates the basic assumption that to actually kill the Warrior at the end of PT2.0, you'll be around the range of level 49-50.

Once finished with the storyline twice through, you unlock Playthrough 2.5, where enemies now scale with your level. Since your expected level is around level 50, enemies will also spawn at level 49-50.

In terms of equipment, equipment generally spawns at the same level you will find enemies in that area. If you have finished the storyline twice and unlocked PT2.5, the level of weapons will scale to your level.

In UVHM, enemies will always spawn 2 levels higher than you, and in multiplayer sessions, will scale based on the HIGHEST LEVELED PLAYER. Meaning, if you have a party of level 50s, and a level 61 decides to join in on the fun, and you're in UVHM, all enemies will instantly become level 63 (highest lvl = 61 + 2 = 63).

Ben Brocka's answer above is incorrect: enemies do scale, at least in some circumstances. Where they scale, and between what levels, seems to vary however.

Some examples:

• I started the Symbiosis mission when I was level 4. Both the Bullymongs near the entrance of Southern Shelf - Bay and the four or five enemies I killed in the town when starting the mission itself were level 3 or 4.

  Just after I'd reached Sanctuary (but before I did any missions or other activities there) I returned to Southern Shelf - Bay as a level 9 character. Both the Bullymongs and the enemies in the town were now level 7 or 8. The loot (excepting cash) and gear sold by the vendors was consistent with this.

  Returning to Southern Shelf - Bay again as a level 12 character, both the Bullymongs and the enemies in the town remained around level 8.

• As a level 12 character, returning to the Soaring Dragon (Captain Flynt's ship in the Southern Shelf), the upgrade seemed uneven; the enemies were mostly levels 7-9, but there were still a few level 2 shotgun midgets and the like kicking around.

• The enemies in the initial part of the Southern Shelf don't level at all, excepting the Bullymongs just outside the passage to Southern Shelf - Bay, which level the same way that the enemies in Southern Shelf - Bay do.