But not all that many or as drastic as you state it.

1. Cadsuane, her strength was actually changed by RJ and that is reflected in Nicola's entry at a level 9 where it also,states she matched Cadsuane. This matches the books.

2. Logain was about to break Nynaeves shield. I see he reason to believe otherwise, she realized it herself in that scene, but he chose not to as he had no chance of escape if he had shown his cards about being Healed.

3. 6 Sisters being unsuccessful in capturing Stonenow or Amalason doesn't speak to strength. It's not like a False Dragon surrounded by his army is going to invite a large group of Aes Sedai in for tea. These men clearly fought back with the OP and likely killed Aes Sedai before any shielding could happen. It works out nicely to the was Sidious explaination works actually.

4. It's not reaching in the extreme to,say Egwene is 80% of Lanfear, that's not some new tidbit people got from the Companion. Many posters in a variety of the boards have theorized this for years. Her statement is clearly a statement on skill and strength combined. She's just spent a few weeks with Moghedien at this point and realizes that the Forsaken can do so much more with their knowledge of the Power, and likely had her head filled with Moghedien's fears about male strength. There is all the reason in the world to believe that she means exactly something different than what Nynaeve did with Moghedien, Egwene has seen first hand what Lanfear was capable of in fight and just as clearly knew that was about having skill and knowledge not JUST strength.

We've been told directly that the scale is linear with an even distribution from level to level, and despite a few instances in the books where that doesn't quite work out, the companion pretty much confirms this. The listings aren't perfect by a long shot, but outside of a few instances there's not a lot of blatantly contradictory information. I'm sorry this doesn't support your view point of the "all mighty" top tier of channelers, but it just doesn't .