Here is a desmos sheet I put together where you can calculate the spd threshold for robin for any number of bird turns in any AV you want.

Setting up for your own use case

To use, simply set the parameters to your setup, for the equipment, slide the bar to 1 if you are wearing it, and slide it to 0 if you aren't. The AV threshold is the AV to squeeze the bird turns in (e.g. 300 for an AA 0 cycle).

For the case where robin doesn't enter fever on her first turn, theres no way of me knowing when she enters fever since its team specific but if you count your team actions, you can work out what character action causes her to enter fever and therefore what AV she would enter fever

Parameters to play with

Interpreting the results

Scrolling down on the side bar, you'll see a column of turns and the speed (at the start of combat) needed for the number of bird turns. The second column is the spd needed if entering fever on her first turn while the second column is the spd needed if entering fever after her first turn (as defined by the AV_team defined in the parameters). If you want to know a number of turns that are not listed there, you can simply click the frst column and enter the number of turns you want to see the spd thresholds for

Note: this is the speed needed at the start of combat, meaning it does not take into account things like the speed from her cone, huohuo e1, etc that applies at the start but cannot be seen on the stat screen meaning thar will have to be manually subtracted to know what speed you need on the stat screen

https://preview.redd.it/j8ojo8o9r0kh1.png?width=1176&format=png&auto=webp&s=13b01875d4cda57a574fc463dddd582aebdfabfc

Limitations:

this does not account for delayed spd boosts, like hyacine e2 without castorice, and also does not account for external AA like DDD or sunday/rmc/etc. This only considers S1 sig, though if you get higher superimpositions, you can open the equation section down the bottom and change how much the sig advances

The math behind it:

the spd needed if entering fever on the first turn was obtained from solving:

AV_threshold= (Action to robin's first turn)/spd + 10000*number of turns/(1.8*(spd+7.6*Amphoreus)

where Amphoreus is treated as a boolean

the spd needed if entering combat outside of robin's turn was obtained from solving:
AV_threshold-AV_team=10000*number of turns/(1.8*(spd+7.6*Amphoreus))

So I got Nicole and am saving for c2 Citlali, and then after establishing a stellar team for a third team to brute force with, I was thinking of vertically investing in Nicole for Chasca. So I put her into Genshin Optimizer to see how worth different investments are and am I missing something or is During not that crazy of an increase for chasca when paired with Nicole and Citlali?

As a baseline, I took the pyro/cryo melt/no reaction damage with nicole celestial skyward and citlali cinder ttds with c0 nicole c0 citlali, c2 nicole c2 citlali, c6 nicole c2 citlali comparing c6 Bennett noblesse skyward to c2 Durin noblesse

	pyro melt	cyro melt	pyro	cryo
both c0	387321	220231	151887	115150
both c2	686477	321449	211628	132129
nicole c6	1031103	576705	317870	237050

Repeating the same with c2 durin noblesse instead of bennett

	pyro melt	cryo melt	pyro	cryo
both c0	478393	234151	187600	122429
both c2	846268	349935	260889	143838
nicole c6	1302401	643266	401506	264409

Durin damage divided by Bennett damage

	pyro melt	cryo melt	pyro	cryo
both c0	1.23	1.06	1.23	1.06
both c2	1.23	1.08	1.23	1.08
nicole c6	1.26	1.12	1.26	1.12

I know Durin also has his own personal damage but is it significant enough to matter when compared to the damage c6 chasca puts out? Additionally, this was done with ttds active which favours Durin as his buffs are non-attack which means the downtime of ttds would be a greater decrease for him compared to Bennett. Also Durin having pyro application would reduce the frequency of pyro melts which would lower the gap further right?

Considering if you were to instead put that 3 cost going from Bennett to Durin into Chasca's weapon, going from r1 to r4 has a 15-17% dps increase for all her bullets across all 3 investment levels and you generally don't consider weapon invest since its particularly low compared to other options, Durin isn't that crazy right?

I see a lot of people talking about how crazy c2 Durin is so I genuinely want to know if there's something I'm missing or if it was just he was a lot better than other options but 2 bennetts just goes crazy