The Chosen Ones

I think it's your computer problem. I play chapter 10 like 7 hours - 10 hours without any problem (except saving time is a bit longer), you may also consider upgrade your warcraft version to latest (I use 1.24e and 1.26a, both are ok).

ya m running 1.26a and have 8gb of memory plus my primary hard drive is an SSD

and the monstrosity i didn't see any number countdown before will check again but mostly when the monstrosity kind a release a pulse kind of blast i get a instant kill some time both phodom and fraz