As you are only L51, you can farm Pete for crystals possibly and buy L50 seraphs in TVHM.
Shredifier is a world drop, so leg loot midgets are probably your most consistent farming source. Ogre drops from boss in final round of magic slaughter, a long slog to get through to him, great gun but it’s work to get it. Other good COM’s drop from the snowman chest, so if the RNG gods aren’t giving you the Leg Soldier you want, you may get something really useful like a Grenadier or an Engineer with sentry and battlefront.
In general, if you are farming bosses, you are actually gaining levels at a good clip. If your goal is to get to op8 hell or high-water, then that’s a good method. Otherwise, take a few decent guns like the DPUH, Kerblaster, slagging gun, and a badaboom and just run through the game dying a lot like we all did at first and just learning how to play UVHM. With some characters (like Axton), I enjoyed getting to op8 a lot more than playing them at op8 and I’m glad I didn’t just sit there and farm the same boss 20 times to gain 5 levels. I admit that I did this a bit for a level or two with the Warrior to gain eridium from time to time, but looking back, there was no need to do that and I would have preferred to gain those levels by playing the game.
Here are some easy to farm items that are quite powerful. Terramorphous and the Warrior are both very easy to farm at L50, but take a bit to get to and some time to kill, even if they aren’t that hard.
Leg Class COM’s (the top row modifiers): Snowman Chest/Tubbies/Loot Midgets
DPUH: Torgue vending machines/Savage Lee
Sandhawk/Pimpernel/Jolly Roger/Orphan Maker: All quest rewards from Scarlett DLC and all easy quests on top of that, just takes a little time to work your way through the DLC.
Bee: Hunter Hellquist/Treeants in the Forest
Once you reach the Dust and its side quests, you can get Lyuda, Hammerbuster, Veruc, Nukem, Slagga or Maggie (depending Hodunk or Zaford).
Badaboom: Need to be at the plot point to get Eridium Blight area, but King Mong spawns in one of two easy to reach locations and so is a quick farm unless you need specific parts or a specific element.