We use Zabbix 3.2 to monitor hundreds of servers and network devices, and we have more than 40000 active triggers.
We have started to play with the IT services feature to create a hierarchy of services, based on triggers.
But it is a pain to configure, as we have to explicitly define all the triggers on which a service depends, and it requires a lot of clicks. It would be nice to be able to set some kind of aggregate trigger on a host or host group, that relates to one or more condition, eg :
IF SEVERITY >= AVERAGE AND "Apache" IN TAGS
That would really extend the IT services feature, and reduce the noise of alerts.