ive searched for this but have only found an answer re. hill troll, which i understand,

but does excess damage by any other enemy go into threat? or not?

ta

No it does not. That is why the hill troll says that as its an exception to the norm. Excess damage is just wasted.

Yes, you can just chump block bigger guys (hill troll excluded)

Meatshields (aka Allies) FTW, like in many games.