A deterrent is better than nothing. It matters much less if it's possible to work around it; and more so that it takes so obnoxiously long to enable it in the first place: i.e, becoming a mentor, or changing your IP over and over in addition to making new accounts, and getting a new payment method.
Time is just as limited a resource as money. The more efficiently we waste his time in his efforts to be annoying, the less likely he is to do so (or the more time we get spam-free). There's no reason they shouldn't focus on banning the mentor, permenantly, his IP, and his payment method; so he has to change all 3, level a new account and character, just to try again, and risk getting again permenantly banned, his character deleted, his payment method banned, and his IP banned. No? How is that not good enough? The only concern is "if its draconian" but honestly if anyone deserves no sympathy, its this guy.