Hi there, I recommend you to take a look at work items / custom domain specific nodes... You can create sync and async workitems to have different mechanisms for retrying an execution. Using script task for calling a web service is not recommened. The reasons are all the ones that you mention. (remember that you are basically coding java inside an XML file). The Error Event is about Business Expcetions / that node can be used to model a branch of the process that needs to be executed on exceptional business cases.. (not java / low level related problems).
Greetings.