They’re worth experimenting with at least. Some of the cannons can be very effective if you can compensate for the slow projectile speed. Some of the SMG and AR types are also quite good.
The biggest disadvantage is the recharge time, which always seems much longer than a gun reload. Weapon proficiency can compensate for that, but it takes a while to build up. (Hint: take an enemy’s health down with a regular weapon, then finish it with an eridian one; the killing shot determines which proficiency the XP counts towards.)
I’ll also add that you can go a while before finding another decent one, so you can out-level them fairly quickly. Well, the green variants at least - I’ve personally never seen any other rarity, and always thought that green was a bit misplaced for how often you come across any of them in the game.



