Don't take my approximations as gospel.
The one thing about the system is that where the challenging/difficult/optimal/easy/very easy/too easy breaks almost seem to be subjective to the skill and the player.
About the only thing certain is that "Too Easy" is after 100%, but not necessarily the "real" too easy (the display is affected by equipment, which may slow skill gains, but many skills you can still get gains as long as the real skill level is within the possibility of a gain.
Optimal, depending on skill, typically shows up somewhere in the 50-55% range, BUT..... I often get my quickest gains on stuff from 40-55% (especially in the crafting skills) - sometimes as low as 35%-45%. So, I'm not sure that the person who programmed the balls (or the item before it that did the same thing) was fully aware of how the gain system worked, and was making their "best guess" at the ranges. (see: Braving Britannia's interviews with the first 2-3 generations of coders, and how the later coders had to deal with code that was barely documented or commented, because of the EA belief that MMOs would be like stand-alones, and have a 6-18 month lifespan, and never last so long that there would be a need to tell a new coding team what stuff did).
That there seems to be such a variation on gain chance from skill to skill, is why I suggested starting so well below the display of "optimal" - as that "Optimal" range for me was always sub-par compared to the 10-20% before I hit it. This is more apparent in crafting skills that start at 0% chance (Smith, Imbuing), than others (like tailoring) were you start at 50% success chance to make an item. I had similar experience training up Mysticism and Spellweaving - the range just shy of optimum gave better gains than "Optimum" itself. In fact, I usually took hitting "Optimum" as a sign to change my Imbuing make item to be more difficult (and used less materials overall as a result, than someone who stayed on that item through "optimum", even though I was using 1-2 more gems each attempt).
But... With Taming, you get a Taming gain generally only on success, so "optimal" might actually be better - yet you can get Lore gains during the tame process, success or fail, so you can start lower.
So, what I'm really suggesting is that you use a Knowledge Ball to see what range you seem to be gaming best on, then use that as your guide -and realize that the range shifts from skill to skill, and might not line up with the terminology of the ball itself.
