Subs do take too long and its particularly irritating in the last 10 mins when its unlikely you'll get a guy on and you're getting a possession penalty.

While I think ping and errors will play a part I suspect that the timing of the sub in the (what appears to be) the 5 minute cycle in matches impacts too. I've not tested whether a sub 2 or 1 mins from the end of the cycle gets on in the next or the one after because tbh I just thought of the above nonsense just now and decided to dump it here. >.<

Being able to toggle the Auto-sub on while watching could help a bit too because my Assistant Coach Otto Teem can often get them on in a minute (server side).