Snowcrows posted a bunch of updated builds with DPS rotation videos just today.
https://snowcrows.com/builds?profession=Engineer
Check out the support builds there for Mechanist. ~25K DPS as a team support. That's good deal less than a number of other support builds. In pure DPS only mode, backed up by a team, yeah, it'll hit ~41K, but browse through Snowcrows and there's at least 10 other builds of various classes provided doing similar damage.
So basically we have a class that does about the same DPS as the top tier of anything else, supports a little worse than other established support specs while doing less damage, and it seems to me that people are basically whining because it's a pet class, and the pet takes pressure off the player in open world, just like every other pet class does, or a any class with a rune of golemancer. Truly, I do not understand what the fuss is about.
There's finally a class that vies for consideration outside of the holy trinity of Guardian/Rev/Necro for raids, and suddenly people start whining about it. The arguments here against the Mechanist are simply not backed up by evidence. It's all just emotionally charged hyperbole.