I don’t think there was any IC designers, but many people on the implementation team have sufficient hardware design expertise, especially an understanding of GPU internals, where I believe the concern on the mining algorithm side is met.
The client implementations (again separate from the mining algorithm) were implemented and looked over between the client teams, core devs, implementors, etc. I believe an audit is warranted for the client code, as one small bug could cause a large disruption to the network, however I also feel as though there has been sufficient review where this may be considered largely unnecessary. But what’s $50k amongst friends? (Better than all those people missing something small I suppose).
The audit also proposes reviewing the technical credentials of the mining algorithm (the part outside of consensus that generates data for consensus to work). This would be handy, but risk is lower because this can be iterated on out-of-band and released to miners piecewise as they upgrade their rigs. They will not do this all at once therefore a risk of total network disruption is small. The audit may be beneficial to ensure code quality and obvious errors are caught, but that’s probably had a fair amount of review at this point and honestly running on a testnet is better. Run it for at least a month on Ropsten with significant enough mining occuring and that is good enough to understand how it works in practice.
Lastly, the audit will evaluate the claims that the algorithm has in terms of utilizing the whole GPU (minus FP functions and some other non-standard things), it’s suitability to the task, any inherent inefficiencies with particular devices, etc. This work has largely been done (ProgPoW Benchmarked, by a Ethereum Miner!). More benchmarking and the like couldn’t hurt, but data collection from the Ropsten testnet with the final draft software configurations is probably the best measure of fitness here. Perhaps those who already have done significant data collection can provide their findings to the auditors and reduce the scope of work there.