Sai is very useful, his ink clones make for a good defense and simple standard attack. If you do use him, his ink clones can only take hit(unless toy have a shield it the clones sometimes). Anko gives him and ink clones a boost in attack when you active the start of her attack. Wind c*so help Sai regain his ink clones with the "Dance of Impetus"(it stops the cooldown of the other ninjas). Also, wind can make clones making it then somewhat a shield for his ink clones.