If you look at this:
https://docs.google.com/spreadsheets...it?usp=sharing
This was what Dervy tested in game. If you look at the 3 second cast time, you have the first 4 break points at 361, 381, 401, 427. In your spreadsheet these are 361, 383, 405 and 427. While the large tiers are correct, every 132 points or every 2% decrease, a lot of the in between tiers are off.
EDIT: Looking at ley lines for 2.5, the points you have where it drops is for the first 4, 361, 387, 414, 467. When I tested huton in game (same attack speed increase) these points were, 374, 401, 434, 467.