Use 1 External IP, Multiple Domains, point to different VIP

First, do you understand the limitations of running multiple ssl sites from a single IP? Your certificate needs to match all names being hosted, or you need to implement SNI

I would use HTTPClass profiles for this instead of iRules in 11.2.1

Create an HTTPClass profile for each website/domain name. Set Hosts to Match Only and put in the host names you want to match. Then set the Action to Send to Pool and select the pool you want to send this hostname to.

After that, assign all of the HTTPClass profiles to the virtual server.