There should be no bad code in production. If a developer knows what (s)he has written, the error should not be too elusive. Proper error trapping for data overflow will remedy this. It is unacceptable to be partial to scripting business logic because the errors are easy to find.

The purpose of ASP is to act as a glue between you business layer and Presentation layer. There is NO justifiable reason to have your asp perform costly business calculations, with the potential for numerous sessions and processes running simultaneously.

A .dll will not hang a web server if it is running in its own process (Isolated). If the timeout is set for the asp and this is exceeded waiting for a response from the .dll then there is the opportunity for the developer to gracefully handle this occurence.