First, that is indeed heel and toe wear and it's not too bad. In some respects, it is normal, especially on driven tires.
No. The shocks may be bad, but this wear is not caused by bad shocks. Bad shocks would cause cupping or some version of irregular wear, such as diagonal wear.
However, mis-aligment can cause more rapid heel and toe wear - which might lead to irregular wear. But since your tires were on the rear, I think mis-alignment can be discounted.
But don't be too hard on the guy at the shop for getting this wrong. Tire wear is pretty complex and even within this thread, there are otherwise knowledgeable folks getting it wrong.
Oh - and as has been said. 15K is a little long to wait for rotation - which is aggravating the situation.