Multiboxers and botters aren't mutually exclusive, anyone saying otherwise never went to Nazjatar or did Tiragarde Riverbud circuit. The problem isn't with your Johnny-40-elems dude running Alterac or instant killing everyone in Warmode ON zones, while he's evidently bringing lag everywhere he goes he's not much of a hassle economy wise. Most of them pay "legit" subs aka from their home country.
We're also not talking about people exploiting the game client to cheat and go under terrain, teleport or using third party tools to dupe gold or items. They're there but in retail WoW their life expectancy is usually short because they're getting flagged and suspended within days / weeks and some of their profit go poof as soon as the accounts got banned.
We're talking about people running multiple 4-8 druid setups for months, years, only to farm herbs / mines / mobs with cheap ukranian VPN subs just to generate gold. They were in the grey area of farming the shit out of the game economy while not having to deal with suspension / downtime because well, they weren't cheating / using exploits (call it clever use of game mechanics).
As
Khane
said they're not really "ruining the economy" especially with megaservers, connected realms, Warmode ON / OFF options. But they're severely hampering your average player ability to gather materials because they're running nodes and mobs 24/7 while the average joe doesn't. That's probably why Blizzard is acting on it. Going on a mundane herb run and struggling to gather anything while watching flocks of druids emptying nodes isn't great advertising.