Greetlings. 
After playing a bard/dirgesinger mix for a bit now, I have a fair idea of how the class works. I can say without a doubt that I love it; both thematically and in gameplay. There are a few issues with the class that have a far reaching impact into how a Dirgesinger can be played, though.
Compared to Bard Song, a Curse Song does not function like an Aura; you need to consume a curse song charge to apply a curse song on new targets that enter your area of influence. This is a common problem between Bard and Dirgesinger, but it is a particular issue for Dirgesingers due to how Curse Song charges are their primary ability resource. To use curse song at its best as a Dirgesinger, one needs to minimise its duration to one minute and use Lich Lyrics every turn, which consumes curse song charges rapidly.
With full replenishment time modifiers applied and being under an open sky at night, a Dirgesinger will replenish two curse song charges every three minutes. These two curse song charges have to supply all of the dirges a Dirgesinger can use, which becomes something of a problem when a cycle of dirgesinger dirges and a single use of curse song can potentially consume five charges in fifteen seconds when the Dirgesinger is hasted. This issue extends further when a Dirgesinger is more likely to replenish one charge every three minutes at best, while using at least one charge every minute.
If a Dirgesinger has spent their curse song charges, their only option is to use a single dirge or curse song every three minutes, or to rest and replenish all charges. This discourages a Dirgesinger from spending their charges on Dirge abilities until a boss enemy or enemy player character appears, or they risk not having enough charges available to perform a full cycle of dirges when they need them. Much of my group play as a Dirgesinger rarely sees me use dirges for this reason, as I am always saving them for an enemy type upon which the consumed charges wouldn't be wasted. With how frugal a Dirgesinger must be in managing their curse song charges, it isn't unusual for me to run an entire dungeon and not use a single Dirge Song, which consistently makes me feel dissatisfied with how underutilised my Dirge abilities are.
I have been spending some time thinking about a suggestion that might address these issues in the dynamic of the Dirgesinger class, which I can submit when the suggestion box is open again. If anyone else in the community has any ideas of their own, please pitch in!
My first ideas reside in making Curse Song behave similarly to Bard Song, so a single Curse Song Charge can last much longer without needing to consume more charges to reapply the same Curse Song to new targets. It might also be advantageous to prevent singing bard songs and curse songs at the same time, although both can apply if two different bards/dirgesingers are singing with each other.
To directly address the Curse Song charge replenishment issue for a Dirgesinger; the Echo ability, in addition to its usual effects, can also consume bard song charges to immediately replenish an equal amount of curse song charges dependent on how many dirges are active when the ability is used. This would allow the Dirgesinger to convert their bard song resource into their primary resource to fuel their abilities, which can be exhausted if they run out of bard song charges. Since Echo is also a level 10 Dirgesinger ability, the capacity to convert bard song charges in such a way is reserved for those that have built around using Dirges frequently.
Finally; Danse Macabre. This passive ability can be considered the signature ability of the class, but it isn't active when the Dirgesinger is only playing a Curse Song. As part of the suggestion, I'd also recommend that this passive is also active when singing a curse song.
What do you think? Got anything to add? What have your experiences with Dirgesinger been? Don't be shy.
