11.4 node/pool select according to domains list

I would add to Kevin Stewart's suggestion: Use an external data group, and use one datagroup for each class of domains. So if you are splitting into 2, one datagroup will contain 500 domains, the next datagroup will contain 500. Also use one pool for each class.

Use if-elseif expressions to match the classes as highlighted in Kevin's example.

Since you are matching domain names, you will need to match by HTTP::host, as that is independent of IP address.

Reference: Irules If and Expressions: https://devcentral.f5.com/articles/irules-101-02-if-and-expressions.UjG3LETK3Fg