Have you tried to execute the same SQL from Toad? Is it fast or also slow?
P.S.
Have seen many times that suddenly execution plan changes (to worse of course!) in one second … so this problem should be eliminated so we can focus on other involved part.
If he’s tried two different versions of Toad and slowness is the same, and files are more or less the same, I’m guessing that something has changed in the database to slow it down. It’ll be tough to execute the same SQL though. Toad uses bind variables, with arrays of 500 items per bind variable to insert 500 rows with one statement. You can’t do that from the Editor. You can do bind variables there, but not with arrays.