By and large I think there is some kind of exponential increase in power as you go up the strength scale, for simplicity let's say power = level squared (thus a level 10 woman can channel 100 units). This would mean that a level 15 would channel 225 units and be more 2x stronger than a level 10. By the time you get to Lanfear you have 441.

Taking that further you can sub-segment each level (for simplicity sake let's use 4.41 per level for 100 levels). If you assume the Bell Curve is based on the original 21-level list you wind up with a M-M-M about level 11, or about 121 unit channeler, just about 28% of Lanfear. Knowing Daigian is very weak for AS, but still stronger than 37.5% we can place her in the Mid-High level 8 section (about 75 units) which also maps to Siuan falling to this level if you put her original strength at the top of level 14 or the bottom of level 15 (around 200 units).

Amys being close to Siuan is also around a 200 and Melaine maybe a 150, which could make Egwene as strong as 350 (which maps to Mid-level 19). That would make:

Egwne/Elayne = Mid level 19 (about 350)

Tamela/Viendra = High level 19 or Low Level 20 (365)

Moghedien = Mid Level 20 (about 375), Assuming Nyn was at 85% of Potential when she faced Mogs this makes sense, and since she's been a wilder for close to 10 years that does seem to fit

Mesaana = Low level 21 (400-415)

Nynaeve/Semirhage/Graendal = Mid Level 21 (Between 415-430)

Sharina/Alivia/Cyndane = High Level 21 (430-440)

Lanfear = Maximum Level 21 (441)

This would map to Egwene/Avi combined in LOC being strong enough to overwhelm Lanfear (assuming they average to 75% of potential they would be about a 475 linked).

Nynaeve is obviously far closer to her total potential than the others (Much like Rand starts out far closer to his potential than Elayne), or she would never have been strong enough to face Moghendien so early on. Equally obvious is that she must be very close to the absolute maximum female strength. IMO Egwene and Elayne fall somewhere about 80% of the max with Moiraine about 45% and the majority of AS about 25% or less.

Questions/Comments on your post I have:

Since when is Melaine only an "average AS"? She comes right out in TGS and tells Aviendha that she is stronger than most AS ...

We also know from RJ that Elayne is one step lower than Forsaken level, by your contention that one step equates to a nearly 50% drop. And then there is another 50% drop before we get to a normal AS.

In TSR Egwene was only a little stronger than Moiraine, and Elayne less than that when she is talking to Rand she notes that Moiriane would be "senseless" if she tried to hold as much of the OP as Egwene was, senseless, not burned out! Of course Rand, who at this point is already as strong as at least some of the Male FS by that point is many times stronger than Eg/El!

And of course you've left out one of the most important quote...

Moiraine's assertion that Egwene and Aviendha combined could overwhelm Lanfear. And this is long before either of them could be anywhere near their Potential! If they were both only Potential 50 they wouldn't have been anywhere close to matching Lanfear, much less potentially strong enough to overwhelm her.

My power ladder on 21 levels would look like this:

Level = Maximum units
1 = 1 *Morgase
2 = 4
3 = 9
4 = 16
5 = 25 *Sorilea
6 = 36
7 = 49
8 = 64 *Daigian
9 = 81 *Weak AS (Siuan, Kumira, Leane)
10 = 100 *Adeleas, Vandene, Carean, Saritha, Temaile
11 = 121 *Average AS/Mean/Median/Mode (Low end = Merilille or Elza, Higher end = Ispan, Falion)
12 = 144 *Lower end = Verin, Alanna, Mid range = Rafela, Masuri, Katerine, Higher end = Myrelle, Beonin, Morvrin, Carlinya)
13 = 169 *Sheriam, Pevara, Yukiri, Saerin *Aviendha at time of Lanfear comparison
14 = 196 *Strongest AS
15 = 225 *Egwene/Elayne at the time of the Rand comparison
16 = 256 *Kerene/Meilyn
17 = 289 *Cadsuane (Egwene at time of Lanfear comparison/Amys and Melaine comparison))
18 = 324 *Bode (?), Nicola (?)
19 = 361 *Egwene/Elayne/Aviendha/Metaara
20 = 400 *Tamela/Viendre/Moghedien
21 = 441 *Female FS/Nynaeve/Talaan/Sharina/Alivia/Sommeryn

Assuming you must be at least 70% as strong as someone to maintain a shield on them this also maps to 3 Sisters holding Semirhage and 2 for Egwene. And it's a 20% increase from Egwene to Nynaeve and a 25% increase up to Lanfear... candles and bonfires... also makes it clear why Nynaeve couldn't easily put a shield on Elayne... she's not enough stronger to simply overwhelm Elayne (IMO must have at least a 50% strength advantage to shield without effort, thus Egwene had no trouble with Sheriam, but may not have been able to weave a second shield strong enough to shield Moria at the same time).

to add to this RJ also claims there are "several levels of male strength above the female levels"

If we make an assumption that there are 25 levels of male strength that gives us Rand at 625 at full potential and places the average male at level 13 (units for men being 6.25 per sub-level for there to be 100 sub-levels; thus a 13 level man would be able to hold more Power than a 13 woman but in effect they are equals)

Level = Maximum units
22 = 484
23 = 529 Asmodean(?)
24 = 576 *Taim? Logain? Be'lal(?), Rhavin(?), Balthamel(?), Sammael(?)
25 = 625 Rand, Ishamael, Demandred, Aginor

This allows for Rand to have had room to grow, but still be strong enough to have faced off with some of the weaker males so early in the series (Basically I think Rand was at 85% of his Potential by the end of EoTW and probably about 95% by the time he went toe to toe with Sammael, likely he's very close to 100% by now.