The primary issue with this is that bitcoin mining as a load is very different from anything else except code-breaking. (Notably, there are no bandwidth requirements at all -- you can feed a bitcoin miner the source data of 32 bytes and employ it for 4 billion hash iterations)
Knowing how fast a card is at bitcoin mining is flatly uninteresting to anyone who is not using it as one.
Not true. Bitcoin mining is a viable benchmark for integer performance, something that is used for things other than cryptographic brute forcing.
Also, the data processed is around 104 bytes (two SHA265 executions: the second part of the first execution for the 80 byte header (hash state from first part + the next 16 bytes) (the first part of the first execution only needs to be done once and is done on the CPU), and then the second execution (hashing the result of the first execution)).
Finding a solution becomes harder with time, but the number of algorithmic checks performed per second is constant (more checks are simply required as difficulty increases).
