To Kerberoz (math geekiness inc): You should specify that those charts are on a logarithmic scale.
Re botting: SE might be correct that they can't do much to detect botting, but they have done nothing at all to eliminate the root cause of the problem, namely world spawn HNM with fixed spawn points and semi-fixed spawn times. Newer style HNM do act to aleviate this slightly with random spawn points and/or longer spawn windows but it still doesnt solve the problem with our old friends in the Aery/Dominion/Valley.
Many people are of the opinion that if you aren't "cheating" (I'll use the term loosely for the purpose of this discussion) you aren't trying hard enough to get an edge over the competition. This phylosophy is as old as competition itself, look at pro sports, politics, industry, among numeous other competitive human endeavors. People, in general, are going to do what it takes to get to the top and that isn't going to change any time soon. Sometimes that means resorting to less scrupulous methods...
So, if they can't directly find out who's botting and punish them, and we can't change 1000s of years or human nature, then the only logical course of action that remains is to fix the reason so many people resorted to botting in the first place, Zilart kings.
EDIT: TL;DR - If SE can't do anything to stop people from botting they should ask themselves what drove people to this and try to change that aspect of the game such that botting doesnt provide as big of an advantage.