Is it necessary to always process that many items? E.g. the smart rule could add/remove a tag (e.g. Excluded) too and this tag could then be used to reduce the number of smart rule results.
I was thinking the same thing when I entered that number 
Should be okay though, now that the trigger is set to “after saving”, right?
My understanding is that there would only be any processing when I make a change to an item.
This should usually process only one item as such rules are only triggered after saving modified documents.
This problem reared its head in my direction. @cgrunenberg I sent you an email with my Activity Monitor output.
DT scripts seem to be the culprit. In my case, disabling all scripts did not work. However deleting all DT scripts did allow me to import my DB without issue (short-term bandaid fix).
And how are you determining this?