Just to point out, you do realize that increased song duration will actually allow you to slot in a bigger amount of time to DPSing?

I forgot how long exactly the song duration is, but- Say the songs last 3 minutes. So given you're playing it safe and keeping two groups of buffs up, you have a window of about 2 minutes to DPS between running and buffing.
Then consider the relic increased the song duration go 6 minutes, you'd still spend the same 1 minute doing the buffing cycle, but now you go from having 2 minutes avaiable for DPS to 5 minutes. A lot more damage-focused.

As you can see, it's an indirect boost to your DPS capacity.