Guardian has some weaknesses

Just my thoughts on the new guardian keystone.

I feel that is procs too easily. Minion damage triggers it and this has been a problem many times. Could we have it trigger off of champion damage only? Perhaps champion and jungle monster but I think it would be best if only enemy champions could trigger it.

Sometimes its pretty awkward to trigger as well as there is only a small window to trigger it unless you're stacked on top of your ally, could the guardian buff last a bit longer then 2.5 seconds?