I find engineering one of those 'primary professions' that could be replicated on most characters someone has, unless you only care for gold making you can replicate those gold-making professions on most characters. Engineering doesn't have much gold-making items, but its utility, transportation increase, gadgets (远程拾取器,移动邮箱) are too useful to not use it as one of the primary professions, at least on some classes. But nevertheless, if you're doing what's on this article, you should have 5+ characters to make it to the profit, but even then, putting, let's say, alchemy+herbalism on ALL those characters would be a waste of time and resources. I myself have ALL professions, Alchemy on 2 characters (both Goblins, for obvious reasons), and only 2-3 of almost 20 leveled characters don't have engineering, and can tackle 99% of the world's profession needs.But people have the choice to do it as they please haha.
I wish I had realized it was Super Squirt day. Last time Wowhead mentioned it was coming up so I kept looking at the new articles to see if it was mentioned. I didn't realize that it's mention would be put in the economy page.