I tray process LF film. Presoaks are always stipulated by the manufacturers, and have never caused me a problem with any of the tens of films and developers I've used. Mottling and streaking are common when insufficient developer is used and agitation is not begun immediately upon insertion. I'd look at what similar conditions may be present in your processor. XTOL works fine (and reliably) with TMAX. Most developers work best when given around 10 minutes (or longer) for normal development.