Whirling Strikes works almost the same as HoF - without Carnage, but with raw DoT. It's def. a great ability. And using one melee weapon and one ranged is smart. I knew that stuff like Riposte works that way, but I didn't test this on Whirling Strikes actually, so good point.
I think the best thing would be to use Fire in the Hole with Chain Shot and Driving Flight. THat would mean 1 AoE attack + 2 AoE jumps per shot. This will generate plenty of hits (33% more than with Minor Blights). They will do a bit less damage per hit than Blights, but you will have a lot more hits and once you use Avenging Storm it's the number of hits that matter, not so much the dmg per hit.
Still, Whispers of the Wind or HoF with Hand Mortar + Fire in the Hole on a crowd is better than Whirling Strikes (even if you can pull it off with one melee and one AoE ranged weapon equipped, you will always miss that there's no reliable AoE on your melee weapon). And it's also more versatile because you can still use it effectively with lets say pistols, fists or sabres when enemies are not forming a tight group. A Ranger is screwed then (if he wants to use Whirling Strikes - same with a Barb).
Also Whispers of the Wind is great with Swift Flurry + Hearbeat Drumming + Wahai Poraga if enemies stand near each other. There will be a lot of additional crit procs that will be AoE attacks as well that will have a chance to proc an additional attack and so on. Still one of the most powerful combos against mobs.