After the most recent hotfix [10/17], Which decreased the magazine size to 1 and reduced the damage by about 30 percent; I decided to do some testing with the flakker on my Amara. I found a few things.
I noticed that the reload animation does not start until after all of the explosions have gone off. However, if you hit your reload button after you shoot, you can begin the reload immediately instead of having to wait. This is important because if you combine this with the phasezerker COM and 5/5 in alacrity, you can speed up the reload significantly and get back to shooting very quickly.
Now with regards to the damage loss, I believe that it isn’t the worst thing for a gun, with as large a blast radius as the flakker has, to not instakill everything within a hundred mile radius. I believe that this weapon is meant to hit large groups of enemies, weakening them, and allowing you to switch weapons and finish them off. It is much better at fulfilling this roll now.
If you get it anointed for increased damage after phaseslam/phasecast, it will once again return to its former glory of being a killing machine.
Give it a try and don’t be too quick to drop it thinking its useless because “useless” is a very poor word to use to describe this beast of a weapon 
Additionally, the devs are aware that it is still consuming 5 ammo per shot and are (most likely) working to fix this and set it to 1 ammo per shot, as intended.
What are your opinions on the Flakker? Let me know down in the replies!