Edit - How far into the game should I be before I mess with any of the DLC areas? I assume they are lootstorms that will fuck the curve up
I did something like this on my last playthrough:
- Honest Hearts after I got to Freeside and did a bunch of side quests around the Vegas area (around level 10-15)
- OWB after doing Boone's quest and a bunch of NCR quests including Camp McCarran and entering The Strip (level 20-25)
- Dead Money after doing the quests involving Brotherhood of Steel, Cass and Veronica (level 30+)
- Lonesome Road after doing pretty much everything in the main game except the endgame (level 45+)
I think the difficulty for the first two DLCs was fine, but I maybe could've started the last two DLCs a bit earlier since Dead Money was pretty easy and I reached my level cap way before finishing Lonesome Road. As far as loot goes, HH has a couple of good weapons and one light armor that are really good but not totally overpowered and which also fit the main game pretty well. It also has a stun gun which is borderline overpowered with the right perks. Maybe there was some doomsday cannon that I'm forgetting but in general the loot wasn't completely over the top or anything. OWB has a lot of pretty overpowered stuff but I didn't really even want to use most of that since the wacky stuff just felt completely out of place in the main game. There's some potentially game-breaking stuff in that DLC, though. Dead Money has one weapon (or maybe two, I can't remember) that many consider to be really good, but I don't think I ever even used it outside of the DLC. Lonesome Road has some powerful stuff, but since you probably finish it last you'll be so powerful anyway that you can just easily waltz through the main game with or without those weapons.
The only DLC stuff I really used in the main game was the stun gun, a pistol and an armor which were all from Honest Hearts. I think I briefly used a couple of OWB energy weapons too. Everything else I kind of ignored or just didn't have enough time to play with, like all the Lonesome Road stuff. In any case, if you finish all of those DLCs, the endgame is going to be a walk in the park with or without those weapons.