i face more and more the same need so i share this idea with you:
I need to graph a ressource for a complete group of server to see if one is below or higher than the group. for exemple lets say i have a physical server with 10 virtual instances and i want to see a graph with memory usage of all the virtual server in one graph. The issue here is that if i add or remove a virtual server i must go change the graph by hand. In a constantly moving virtual setup this is quite impossible to maintain.
The feature that would be handy would be a group graph feature. You choose a group and an item . Zabbix would automaticaly build a graph with all the host that have this item on one graph choosing random colors for each one.
There could be some added thing like graphing the avergae of all those items. This would make group monitoring very visualy easy.
What do you think of this ?