DRG is unbalanced and desperately needs a buff.

[Aegis]

While yes, MNK dps relies heavily on greased lightning - they are still far superior to a DRG by a long mile in practically all content at the moment. (Aside from maybe Garuda?)
There are few, if any fights where a MNK isn't able to maintain greased lightning. At least not often enough to warrant choosing a DRG over a MNK.

Ifrit: Lose GL when he charges. He does this every couple of minutes
Garuda: Lose GL when she jumps or spawns sisters (Jump every minute in phase 1, sisters every 3 mins or so in phase 2)
Titan: Lose GL on bomb spawns, jumps and gaols.

WP: Lose GL on Giant Bavarois when he targets you
AK: Lose GL when targetted by Anantaboga

Chimera: Lose GL when targetted by Chimera
Hydra: Don't lose GL unless voidzones are particularly unlucky

Coil Turn 1: Don't lose GL
Coil Turns 2-5: (I don't have enough experience to comment)

Now everyone loses DPs when they get targetted by Anantaboga, Chimera, Giant Bavarois, Titan etc. the difference is that Monk then needs to spend 9 GCDs to get back to their optimal DPS state.

Perfect balance can be used to counter this, but only once every 3 mins (iirc) and it still takes 3 GCDs to get back to GL3 with PB active.

[Altena]

Ifrit: Lose GL when he charges. He does this every couple of minutes
Garuda: Lose GL when she jumps or spawns sisters (Jump every minute in phase 1, sisters every 3 mins or so in phase 2)
Titan: Lose GL on bomb spawns, jumps and gaols.

Ifrit: Yeah you lose @ charges but they are pretty far between each other (every few mins). Aside from that he is a tank & spank, so for a good portion of the fight you have T4 GL.
Garuda: As I mentioned, probably the only fight where DRG excels.
Titan: You can hit/ws on the bombs to maintain GL. Jumps are fast enough to maintain GL. You lose if you get Gaol'd but that's 1 in 7 chances every minute or 2...

WP: Why? Switch to FoE and tank it.. Problem solved.
AK: 1 in 3 chances that you get an orb on you.. Once again, pretty low chance.

Coil Turn 2 is stupid for melee in general.
Coil Turn 4 is consistent and pretty impossible to lose GL.