Yes she has been underrated from the start but the thing is hinata is not weak she just lack confidents and she is too soft she lack conviction in her striks her father has seen this thus decided to name her sister the next head of the household but later on he has seen her progress further and seen she has more confidence but she still lack that conviction and that is why he did not pick to lead the clan on the battlefield but during the war she has kinda come out of her shell fully and being more assertive. Her fully potential is still unkownn I would not be surprise that she is on the same level as nija or far beyond.. That new jutsu of hers the twin lion fist not much is know of it and so far she is the only one I have seen used it .........there is a jutsu she used back in naruto wish she would used it her version of the rotation