It'd probably be worth auto-extracting the response time into a field so that whenever you search for sourcetype "sfe" you have a field that represents response time.
Then you'll have a field that you can perform statistical commands on, such as max, min, avg etc.
With that in mind I'd create props.conf entry to hook into sourcetype sfe. Something like the below:
props.conf:
[sfe]
EXTRACT_sfe_resp_time = ,(?<resp_time>\d{1,6})ms
Then you could run your search through a timechart command something like this:
sourcetype=sfe search.action | timechart avg(resp_time) by host
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