You can’t compare BL2 loot pool with BL3 they way you’ve presented it. I mean you can, but it’s ultimately irrelevant because all you need to do to get the best gear in the game is have a few diamond keys and loot the diamond room. Grab a Plasmacoil, whatever grenade mod suits your fancy, and a shield for s and g’s. The use 5 keys on the first Vaultcard to get a Super Soldier shield. Repeat whenever you feel like it.
At that point, most other gear is just something you came across and looks like fun. Basically, you make farming in this game fairly nonexistent with how easy it is to get the best legendary gear in the game as long as you have access to sanctuary. So a loot pool on a raid boss is just there to be there.
After saying all that… I completely agree that the Guardian Takedown raid boss loot pools suck. Gearbox really needs to figure out the meta weapons prior to finalizing a game. Then put the best of the best behind the hardest content. And they need to have a higher penalty than 5 keys to get the best gear in the game from a Vaultcard.