Manguadi
Dalayan Beginner
Wait, what? Either you left out something that would make this less confusing, or the last line there contradicts everything before it.
Say for example, tier 9 fight X drops a 5% +aggro tome and tier 11 fight Y drops another 5% +aggro tome, and these tomes stack. But you say, if the more-difficult-to-get tome is equal to the easier-to-get tome, "risk v reward gets all screwy". And this is your reason for assuming higher tomes must get smaller. Therefore, the tome from fight Y should be smaller, say 1%? I'm not sure I follow how more difficulty for less reward is less screwy than an equal (but accumulative) reward.
Everything before the "If it's more difficult to get a second tome of equal value, then risk v reward gets all screwy." line is exactly what I would argue for there being no reason to assume that tomes in a line must get increasingly small.
The risk v reward comment was just a consequence of the previous.
Risk v reward is screwy because a 6% aggression tome + a 5% aggression tome is vastly different than either by themselves. Getting a 6% aggro tome is not as big a reward if you haven't already gotten the 5% tome. You have to design it with the previous tomes in mind, since they stack, but the reward is not nearly as large as it is designed to be.
The problem I was addressing was in the very first line, which is that the more points in a line, the more powerful the line. So designing progressively increasing tomes cannot last particularly long, but designing progressively decreasing tomes can. It's just that getting bigger is much worse for longevity, and does nothing for creating balanced rewards.