It sure seems like hub drives have a lot more problems than mid drives.
thats odd. I have been selling hub drives for 3 years, and not had one issue with the motor. (have had several issue with free hub bodies, but that is not motor related - and only on one brand.) Another dealer friend has been selling them since 2010, and he says he hasn't had one issue with the hub drives in all that time. I only recently started carrying mid drives this past year (Yamaha ebikes), but have seen two other brands of mid drives come into my shop for repairs. Maybe its the on-line brands that you are seeing some issues with. When I speak to other bosch dealers, specialized, or brose, they tell me about issues all the time with the mid motors. Hence why I kept shying away from them, until Yamaha finally came out with theirs this past year. Being a larger than $14 billion in annual sales firm, with a long long history of ebikes under their belt, (invented first ebike in 1989, and marketed their own ebikes starting in 1993 in Japan, 6 million mid drives sold), and 3 year warranty, I felt the risk was less than other mid drive brands. Their entire line up of motorsports products have a reputation for quality.
Here's one of several forums regarding Bosch motor issues over in the UK. Seems like a lot of issues to me, and since there are 10 times as many ebikes sold in Europe as here, its probably a more reflective indicator of potential issues since they have been selling them there longer and enough time has passed to start seeing potential for regular occurrences.
http://www.pedelecs.co.uk/forum/threads/bosch-ebike-motor-reliability.29700/. With only about 150,000 to 200,000 ebikes sold each year in the past several years here in the US, and less than 30% of them being equipped with mid drives, thats a pretty small sampling. And given than more than 20 million hub drive units per year are sold for just the China population only, and at very very low prices, the few units we hear about having issues, seems like a pretty darn good reliability reputation. Spend just a little bit more for a good quality hub drive, and the reliability goes up immensely. So you have to put things into proper perspective and context, before you conjecture about what something 'seems' like.