I have a ton of questions about WPM myself much like yours. I'm having a hard time understanding what factors make up the load a player is able to handle. How much does that load have to do with the load on the poller is reporting into? How much of the load is caused by the transaction? Do more synthetic users equal more availability?
I found transaction steps that were being "skipped" or perhaps a better way of explaining what was happening would be that a transaction would fail and when I'd go to look at the error screen shot I'd find a picture of the first step. Almost like WPM wasn't waiting for things to finish, or was falling behind. Support told me to add in 30 second wait times which I replied with... If I have to add in a forced wait, doesn't that mean there is potentially a problem with what WPM is doing?