Bulk binding is useful to speed up multiple individual statements by reducing the context switches between the PL and the SQL engines, but in this case you have a single UPDATE statement, so context switches are not a factor and thus I don’t think bulk binding will help. In fact, I guess it would be slower.
You will probably be able to improve the response time by adding (if they are missing) some indexes.
For example, indexes on the following columns would help:
CLIENT.CLNTNUM,CLIENT.DOMAIN ( or maybe domain,clntnum )
“<i>I don’t have access to Oracle so can’t check my thinking</i>”
So, is this just a theoretical discussion ?