Because it doesn't really need it? We already got our damage buff, and it pretty much made it reasonably balanced. Yes MNK is still more effective in every turn of the 2nd coil, if played correctly. However for the most part - DRG's damage is on par (or at least close enough to).
What you mentioned is "working as intended" though.. MNK is sustained damage over a long period, and DRG's damage is primarily spike. Straight zergs where DPS can stay glued to the mob (like T8), MNK will most certainly be top DPS. Fights that involve a heavy amount of disconnects (Let's say, many of the Primal fights with long animations or jumps/dashes) where GL will fall off are a different story.
I don't care for a DRG damage buff. I don't really think it needs it. It did (and it got it) and while it may still be under what it could be - it is pretty much fine for now in comparison to other classes.. If you were to go down that route, I believe that MNK should actually be taken down a notch (Incoming flame from main MNKs). SMN is in that category as well. Although I consider myself a main DRG, I don't really care if their damage is considered "lower" then a certain class, as it just makes me work harder to pull my weight..
This thread isn't about a huge damage buff for DRG, get that out of your head. It is about making a skill that is in our quiver, something that can be used without unbalancing any classes, add a little flavour/playstyle, and reduce the downtime during disconnects.