Tayuya may seem pretty weak, as the only thing she has going for her is her flute. But she is as strong as a jounin level ninja. She doesn't really add much to the Sound Four but her foul mouth, strength, and the techniques she performs with her flute. She is always constantly yelling at Jiroubou. But even with her great strength and ability to control and summon ethereal spirits, she still lacks a lot in taijutsu and ninjutsu. She mainly uses genjutsu and her flute in battle.
Tayuya is not all flawed, she does of course have her special summon of the Doki; chakra eating spirits which she can control with her flute. These summons can attack and eat at a opponents physical energy with the whims of a note. Her physical strength is also great (like most of the Sound Four).
Not much was said about Tayuya, but she did put up a hell of a fight with Shikamaru. She went into the Cursed Seal's second stage and trapped Shikamaru in her genjutsu and she came very close to winning the battle. She also had enough strength to dispel the bind of Shikamaru's shadow bind technique.
What she really lacks in is just basic tactics and strategy, and she is lacking intelligence so she can be tricked very easily by those who escalate her own intelligence. Other than that she is pretty strong. She is also as Orochimaru said, the only member of the Sound Four who doesn't "slow down the group" other than her "doesn't-want-to-lose" mentality.