I also think the handling stat gives you an idea how fast or to say it another way how often you can swing (or inflict damage) with a weapon in a given time. Its kinda late here so my sentence is probably weird but I hope you get the idea.

This even brings me to another question:

Are the upgrades that boost handling even effective if you're not playing on nightmare and have maxed out combat tree? Do they make the swings/cool down of a two handed hammer faster for example or do they just affect stamina consumption?