I wouldn't do that.. .usually the compo is - roach/hydra/viper or swarm host/corruptor/viper or hydra ling viper.. never seen infestor/viper before but i guess if you're quick enough to learn and use more than 3 hotkeys while attacking, then you could use hydra/broodlord/viper/corruptor/infestor.. in that case, id put viper on the same hotkey as hydra coz viper would be abducting units to hydra and hydras dont have any active spells, just the attack.
I've seen this in ultra late game stuff. I cant tell whether its simply because the vipers were left alive after a transition into infestor ultra or whether it was specifically desired to have both. AFAIK it was used to blinding cloud the stalkers while voids were hit with fungal so they could be hit by the hydras. There were only a few collos out at the time, which might have been important. Was an NA pro of some description laddering.
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