If I may, I'd like to invite you or someone on your team to read a couple of chapters of John Reppy's Concurrent Programming in ML and try Vesa's excellent delivery in https://github.com/Hopac/Hopac.

I'm not clear if you absolutely have to use TPL but CML is likely just a better model for tackling concurrency and Hopac is orders of magnitude more efficient than F#'s async.