While working on a new tamer I've kept a log of my gains. One characteristic pattern is what I would call 'lumpiness'.
Ever so often I have to tame *a lot* more animals to get a gain, than what I would expect from the previous gains. Example: Between 90 and 91 I would get a gain on every 7 white wolves - on average. However, 5 of those gains required only 1-3 wolves, while one gain required 23 wolves.
Lumpiness. Or walls.
Another observation I've made is that these walls can often be climbed by taming another type of creature. Example: From 89 to 90,2 I tamed Great Harts. To get from 90,1 to 90,2 I tamed 14 great harts, then one white wolf.
The gain for 91,9 came on a gaman after taming 16 white wolves.
For those who know something about statistics, you'll know that such a phenomenon could arise by chance and biased observation (we tend to notice 'noticeable' events). That gain for 91,9 might have come from the 17th white wolf, and I wouldn't have noticed it. However, variation have always seemed to help me get past these walls. If the bulls won't budge, try something else. Remember: You can gain from a wide variety of animals / monsters at any given level of skill. We just tend to focus on the docile ones because they are more convenient for training purpose.