Web scenarios do not provide Real User Monitoring (RUM), where a scenario runs in a fully-blown Internet browser engine.
A web application with an authentication procedure that requires to get a salted hash POSTed connot be monitored by Zabbix.
In the past I've seen things like these only now and then. Meanwhile, I'm encountering more and more web services that cannot be monitored with Zabbix.
So, how about adding embedded script support on step level?