I think his "calm" running speed needs to be reduced. It's all about realism right? How can he walk at such a ***** pace with those giant metal hands of his? His enraged speed should stay the same, though.
In any case, when one appears, just try to get out of there, or have everyone throw as many grenades as they can. This is really difficult on Labs, though, especially if you took residence in that little U shaped area of the labs.