Thanks for the thoughts. Let me answer to those.
1) That's something I could do but it wasn't really the goal originally as what I wanted to test was not so much the latencies of connection establishment (TCP Handshaking) but rather an HTTP service itself. I will give it some thought though.
2) I explicitly wanted to abstract the concurrency away from the user of the tool. The API is simplified purposefully. However, I am not sure why you think the requests are sequential. Have a look at this line of code https://github.com/tsenart/vegeta/blob/master/lib/attack.go#...
3) Agreed. I have to think the best way to fit this into the targets file format.
Cheers