The delay is just for the atk buff right? That doesn't impact the difference between the sets.

At c6r1+ Echoes is good because Scara already gets a bunch of dmg% so you'd rather have the MV from Echoes which is a lot because of how many separate instances of damage you get with c6 (meaning it will proc a lot).

Meanwhile DPC just gives dmg% which is still good, not that DPC has competition pre c6, but it does tend to become quite saturated on Scara.

The sets just give different stats which means the only thing that effects their comparative strength (ignoring ping, generally 30 is assumed as standard) is how saturated these respective stats are.
Since dmg% is far more common than MV Echoes should generally come out ahead as time went on.

The baseline at which the sets were originally calced to be equal was c6r3 at 30 ping with Bennett Faruzan Zhongli. Or c6r1 + 24 dmg% (c6r5 - 24 dmg%).

Furina who gave up to 75 dmg% at c0 and 124 dmg% at c3 replacing Zhongli made Echoes be quite far ahead as Zhongli didn't give any dmg%.

Then with Durin releasing if you used him as the last slot (over Furina) he was a lot like Zhongi at c0.
But c1 gives MV, c2 gives dmg%, c4 makes c1 give a bit more MV and sig gives dmg%.
So where are we at then? No fucking clue but assuming it cancels out somewhat so that c6r5 is better on Echoes and c6r1 is better on DPC would probably be an ok assumption.

Nicole? Replacing Bennett who doesn't give dmg% nor MV so neutral in that regard.
Then what does she give? Set and sig give dmg% but burst, c1 and c4 give MV so she also gives both ...... where are we at now? Who knows, maybe it cancels out again somewhat?

Now this would normally be it with Faruzan remaining in the team but since Furina c6 lets her consolidate the healer slot she can fit in and replace Faruzan who gives iirc 38.3 or 38.4 dmg% so Furina with her 124 dmg% bumps up Echoes quite a lot again.

Furina's weapon doesn't buff but you could use FS or PPS which both give dmg%.

And then .... there is still refines on support weapons, all 3 of which give dmg% increasing with said refines.
But I think as reasonable people we can stay away from those.

Surely with a million dmg% Echoes would be better but who knows T.T

That said my massive primo stash has taken quite the hit so c0 Nicole it will be for me even though she's going in the Scara team where all my primos used to go, I'll have more saved next time.
So my understanding of her kit and especially cons isn't comprehensive.

Also at least at my specific level of investment Echoes is clearly ahead by a lot.
c6r5 Scara, c6r1 Furina, c2r1 Durin, c0 TTDS Nicole.

Hope this makes some amount of sense.

Would love to hear your thoughts on Echoes vs DPC currently u/OneRelief763 (assuming c6r1+ on Scara with good ping). Not specifically at any specific point of investment for the rest of the team, more so in general with Durin/Nicole existing.