Not really. If you buy a player as backup or as an investment in the future and they don't hold down a starting berth, that doesn't make them mistakes or a waste, especially if you sell them at a profit. They served (or are serving) their purpose as intended.
Karius is the only one on the list I would class as a complete failure and waste of money, but even that was a limited loss in financial terms (excluding the financial impact of possibly costing us the CL final). Keita could be the biggest mistake by a mile, but I think its still far to early to say. Hopefully he'll come good but given the crazily successful run of significant transfers we've had over the last few years, we must come a cropper at some point.
Now if you went back a few more years then you can really start talking about wastes of money..... Balotelli et al