Well the Sound ninja 5 still have their Curse mark forms, and they all had special abilities. Sakon/Ukon can fuse into other ninja's bodys. Tayuya can summon giants and use powerful genjutsu. Jirobo is very powerful and drains chakra. Kidomaru Is a great long distance fighter who even found the blind spot of the Byakugan. I don't think this fight would be as easy as it sounds.
How those other gennin/chunnin sound ninja were beaten...
Sakon/Ukon : They were beaten by a combination of crow and red ant , and were beaten by kankuro. Sakon/ukon didn't even had the chance to even fuse/attack/defend.
Tatuya : She was beaten by temari by a powerful gust of wind, killing her instantly , before she had the chance to do a thing.
Jirobo : He was beaten by choji..
Kidomaru : He was beaten by neji with difficulty. His main attack style is by his webs and arrows , which have a chakra base. His attacks can also follow the target. He fights from a range distance.
How akatsuki kills the weak sound ninja
Sakon/ukon : his main attack is fusion and curse mark .....
How he dies ;
-sasuke would kill him instantly with his amazing speed before anything happens
-Itachi is formiddable at gen jutsu , he can just place a genjutsu on him or kill him with his epic speed.
Tatuya : Her main attacks are giant golems ( she only have 3) and gen jutsu.
Do you think giant golems would affect the akatsuki when some can fell tailed beasts?? Some people are very fast in the akatsuki, again they can fell her in a blink of a eye.. even if she manage gen jutsu , do not forget itachi is a master at it too , and such genjutsu of that level would not affect him.
example : kurunai vs itachi
jirobo : He can drain chakra and have super strenghth..
Do not forget he is not quick , again it is won by akatsuki. Speed > raw power
That have always been the rule
kidomaru : webs and arrows that can follow the enemy and have a chakra base..
I am not even going to bother how he fails so epicly and dies.