Thanks for your suggestions but it seems more like a proactive solution, while I need to do this retroactively as my campaign has been running since October.
I don't think there's an out of the box solution for this - the smart campaign will tell you how many leads are in a wait step, but not who.
I would probably implement what Jeff suggested. From there, you can go back and see which emails have been delivered to leads and mark them with the appropriate Wait Step value.
I am also interested in a simple way to view this.
The workaround if there is not an out of the box solution is having a field that is updated based on what step they are at in your workflow. E.g. before your second wait step you could update a data value on a custom field called "Campaign Step" with a value of "Wait Step 2". Then before sending the email update with "Email 2 Sent" etc.