Have you played any other classes? Because the same thing is true for literally every class in the game.
For example, MNK:
MNK DoTs:
Touch of Death = 270 total potency (over 30 seconds)
Demolish = 240 total potency (over 18 seconds)
Outside of those attacks, MNK's highest potency attack is 180.
BLM's DoTs:
Thunder 3 = 340 total potency (over 24 seconds)
That's even higher than Flare!
In fact, all DoTs have higher total potency than standard attacks. And there's a very simple reason for that. Using DoTs requires you to balance the effects over time vs. the benefit of an immediately strong attack. If the mob is going to die soon, then you want to skip the DoTs and use standard attacks. But if the mob is going to live for a long time, you want to use the DoTs. If DoTs were just as strong as standard attacks, there would be literally no benefit to ever using DoTs.
In other words, if the DoTs were as strong as standard attacks -- which is what you seem to be asking for -- then there would be no reason to ever use DoTs. SE should just take them out of the game. Because why would you use an attack that does 150 potency spread over 30 seconds, rather than an attack that does 200 potency immediately?
Moreover, as you admit, most of DRG's damage does not come from DoTs. Most of their damage comes from standard attacks. And DRG's combination of quick buffs and powerful attacks with longer cooldowns means that they're geared toward spike damage. The fact that their highest potency attacks are DoTs just means that their DoTs are useful; it does not mean that DRG is only a sustained damage class. It means they can continue to do sustained damage even when their "spike" damage is on cooldown.
As Hyrist said, I think DRG's have great utility right now. The fact that their piercing debuff helps BRD, too, is huge, especially considering that BRD is probably the only DPS class that's considered practically mandatory for the Coil right now.
But I would be curious how you think they can add utility to DRG. I'm generally in favor of making classes more useful. If you can suggest a way to make DRG more useful to a party, I'd love to hear it. But it sounds like you're only disappointed that other classes are parsing higher DPS than DRG on certain fights. If that's your complaint, then I'd respectfully suggest that you worry more about winning fights, and concentrate less on who's parsing highest.