it dosent matter how long he caught ginkaku,the fact is his shadow was fast enough to catch him,if his shadows came from being easily dodged by hidan to catching a 6tk opponent,then he has improved a lot,which means catching hidan or kakuzu while behind gaara's sand isnt gonna be hard.He caught Ginkaku for like a second. Hidan and Kakuzu were handily kicking Asuma's ass with backup from shikamaru and those 2 chuunins. Hidan was almost soloing. There is not much from Shikamaru showing a huge difference in strength since then.
Man there's a lot to counter here, though I would like you to prove all these claims with chapters and pages.
In the meantime, here's a refresher on the scale of Kakuzu's jutsu.
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No, I do not think Gaara wouldn't be able to defend against them but they would work as good distractions and would require Gaara to use a lot of sand.
Oh yeah, @ the scans Joki posted above, do you see the size of those lightning spears?
Asuma is a closed range fighter,those other two were just chunins,gaara is neither of those,he is a mid-long ranged fighter and a kage,
when gaara was fighting kimi,his shield of shukaku was made from crushing the hardest minerals in the ground,and compacting it with chakra. If he was able to do that at 13,crushing kakuzu's stone skin isnt gonna be hard.
Gaara wont need too much sand to defend against them,he can even let his sand clone use sand to block the attacks,the only time he has used large volumes of sand is to protect large goups of people,his village from c3,his dividion froom joki boy and the meteor,he has only shika to protect,a fairly large sand wall will survice,he can manipylate it to block any of their attacks in any direction,and those distractions wont help much cuz gaara's sand blocks attacks automatically. Those lightening spears are blocked by a sand wall.
Kakauzu dosent even start out with his hearts out,if he gets sand coffined,he is dead. Hidan isnt gonna touch shikamaru,those shadows have gotten much faster and wider,he wont even know what they do,until it hits his shadow,are you telling me he would know to protect his shadow with no intel?
Gaara can use the sand under their feet to attack the hearts if by chance they come out,by that time,it would have been turned into a sand box anyway and they would loose.