how can I view the top 10 talkers' IP addresses for a given timeperiod?

Since you ask for the past, I think its doable with 2 options (from what I know), either with logging using an Irule or using the Analytics (AVR) module.

As you also called netstat, which is a real time data, not of past, I'll share few commands which I use, You can try these options,

Current Connections for a given VIP:

tmsh show sys connection cs-server-addr <VIP> | head -n -1 | tail -n +2 | awk '{print $1}'

You can add more filters like awk, cut, sort, uniq to find top source ip's consuming your respective vip.

Total Connections Count so far:

tmsh show ltm virtual <Virtual-name> | grep -E "Ltm::Virtual Server|Total Connections" | awk 'NR%2{printf "%s ",$0;next;}1' | awk '{print $3","$6}'

Live Connections Count on the box:

tmsh show ltm virtual all | grep -E "Ltm::Virtual Server|Current Connections" | awk 'NR%2{printf "%s ",$0;next;}1' | awk '{print $3","$6}'

Also you can use bigtop command,

bigtop -conn -once

Hope this helps.