It was already shown Amaterasu can't burn through Gaara's sand so that point is moot.
As for the levels of Susanoo, I am not saying Madara's lvl 3 Susanoo > Sasuke's lvl 4, but I am definitely saying 5 of Madara's lvl 3 Susanoos > Sasuke's lvl 4.
Where did Sasuke use Amaterasu offensively against Gaara? . He only used an Enton to guard himself, not to mention Enton has different properties based on Sasuke choice of manipulations. Also, Enton Blade>A Ball of Enton.
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Against A it had piercing properties.
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Enton Blade pierced right through Zetsu, pinned him to the ground and lit him on fire.
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Enton Blade is still a blade so don't forget that it has cutting and piercing abilities.
Smaller version of Enton Blade cut Kidomaru's Senjutsu enhanced webs used by Kabuto.
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Lol, no. 5 lvl 3 Susanoo clones can't even scratch any lvl 4 Susanoo that has ever appeared in this series. Lvl 4 Susanoo is superior in this situation because it has more strength behind its swings than a lower level Susanoo.