I think their ban procedure is heavily related to the Ban reason. If you are being investigated for Gold trading / Selling, using different pcs under the same Ip won't help you.
At least it didn't help me in the past. And I used 3 different Pc's. You won't dodge a manual investigation by a GM just with that.
Using an IP changing service is also a HUGE pain in the ass. Stupidly overused Ips that will get you flagged and banned within hours, lying vpn sellers that promise you a dedicated and completely new IP....and it turns to be an already known and flagged as Spammer Ip in most filters.
Also, you need to use a "self disconnect" service that will auto turn everything off when their servers are down, even for one second.
It is well known a drastic change in IP range location is one of the fastest ways to get Blizz's attention. And , I've tried several Autodisconnect programs. Even the slightest delay in them, or a failure by them, or you not remembering to turn them on, will flag your Pc for investigation.
Bottomline is,the point where you realize you need to change IPs is a real pain in the ass.
Is the Rubicon of botting; if you get through it, you could expand without limits. But it is superbly complex, has lots of complications and most people stop at this point when facing the related issues.