How are they "messing with our expectations" if they posted a video doing actual size comparisons of the product?
That video wasn't linked in the first post or the linked product page. I agree that the video gave a far better visual indication of the size then the product page. That product info is what's being copied in webstores, the images with the dimensions is all the way to the bottom of the image list.
Writing/making ads has it's own science behind it. This ad/product page indicates that the mimic is big, how big? They only list the biggest dimension in the text on the product page (20"). That leaves the consumer with it's imagination. And even the video doesn't show the product next to an adult of average height, all the shots are made at angles that make it look big besides things that make it look big.
Imagine me sending instructions to a sawmill, stating the the plank needs to be 20" high and then hiding the rest of the dimensions somewhere in an image gallery that has a pretty good chance of being overlooked. Do you think I'll get a plank that has the 'hidden' dimensions or just 20" tall and some random other dimensions? This is how the average consumer looks at these kinds of product pages.
This is not the first such a D&D/Wizkids product page I've seen. Often Wizkids painted miniatures even show colored renderings of the minis instead of the actually painted minis... Some product pages inform the potential customer of ALL the product information and try to sell the product to the potential customer, in this case they are just trying to sell you on it.
The most instructive image for a potential customer is making a photo of an average sized human holding the mimic. Straight on, no special lenses, etc. It's not there.
I know how Wizkids operates, so I'm way less surprised then someone who first reads that, then actually does the math and realizes that it's far smaller then they first thought. We all make mistakes, it happens. But people become pissed when they realize that the ad/product page was written exactly like that in the hopes you didn't do the math (or scrolled all the way down in the image gallery). People 'complain' not because it was a honest mistake, but because the company is trying to mess with you to buy an expensive product.