Multiple ISP Gateway Outgoing iRule

Please correct me if I inteprete it wrongly,

If Gateway_Pool_1 is up, each HostGroup will use its own Gateway_Pool as outgoing, and Gateway_Pool_1 also act as default outgoing.

If Gateway_Pool_1 is down, all hosts regardless which HostGroup will use Gateway_Pool_4 as default outgoing, and this would cause ISP 4 congested.

Can I replace the it with the following iRules to only use the default Gateway_Pool_1 if individual ISP gateway is down? 

Your correct in your interpretation and your revised iRule code appears valid.