Hi Josh,
I don't think there's a better way to do it than a smart list. The challenge is that MSI emails can be individually customized by the sales rep, and often are - so even though the template used may be the same, the actual email content is often different. I believe that's part of why there's not a separate Sales Insight Email Link performance report like there is for regular Marketo emails. If the content you're sending is identical to each recipient, it may make more sense to create a campaign with the trigger "Campaign is Requested; Source: Sales Insight" and then have the Sales Rep request that campaign instead.
Grant