Does the Dark Knight need a Boy Wonder? Yes, indeed.
The Dark Knight had always needed a Robin since his first appearance in 'Detective Comics' a year later of the introduction of the Dark Knight. And from that point on, all the Robins that came and went, had either a small or huge pivoted role in the development of who Batman is and what he stands for.
50 Shades of Gruesomeness
Whether there is a Robin fighting alongside him or not, he plays a great role in how Batman punishes the criminals that infest his city. Think about it, whenever Batman is fighting crime alone due to Robin leaving for a certain reason or dying, Batman tends to go a little overboard with the criminals of Gotham City. For instance, this fact is shown in 'Batman Vs Superman' and 'Death of a Family', when he started to brand his victims and leave criminals (whether they actually deserve it or not, depending on the crime) near the point of death. In both of these comics, Jason Todd (the second Robin) was brutally killed by the Joker which is unknown in the movie by what methods but in the comic, he was murdered with a crowbar and then later a timed explosion.
Another point that 'Death of a Family' brings is that once Tim Drake took up the mantle of Robin, Batman gradually stopped being too gruesome to criminials, whether it was the presence of a young boy that wanted him to make it a little PG-13 or he wanted to be a positive role model for him, he just stopped.
A Helping Hand
Another reason Robin is so much needed is that he can actually help Batman out and ave him. Whether it be in the comics, video games like 'Batman Arkham City' or TV shows, Robin always helps Batman out. Whether it was a rare miscalculation by the Detective or something had gone wrong, Robin had always came helping Batman.
For example, in 'Batman Arkham City', after Harley Quinn kidnapped Batman for not being able to save the Joker from dying, Tim Drake who was the Robin at that time in the game, came rescued him, depending on if you can get past all the obstacles in your way.
An incident that shows Robin's much needed assistance is that when BOTH Nightwing and Batman were stuck and ambushed by Two-Face in 'Death of a Family', Tim Drake came and saved them both single-handling. Though, it wasn't that big of a deal.
In the years after the Robin's first appearance in 'Detective Comics', there had 6 different Robins, each playing a large role in Batman's legacy (except for Stephanie Brown). Ha. Ha. Ha.
Sometimes these large roles can be anything from taking up the mantle of the Dark Knight to helping him fake his death.
In multiple times in the comics, a Robin would become the Batman, depending on what universe. For example, in 'Batman R.I.P.', Dick Grayson, the original Robin become Batman when he was dead, however,on the other hand, in 'Damien: Son of Batman', Damien became Batman when Dick Grayson was killed by the Joker and Bruce could no longer be Batman due to his age.
Another Robin that played a pivoted role was Carrie Kelly who played a huge role in helping Batman fake his death in the comic book ,'The Dark Knight Rises'. She managed to get all of the Sons of Batman in the destroyed Batcave and dug up, Bruce Wayne from his grave. This death was much needed as the government had forced Superman to bring Batman in and this was the safest play.
So all the Robins played a role in how Batman came to be who he is now and what he stands for. Whether it be making him less gruesome, giving him a helping hand when he needs it or continuing his legacy either by being the Dark Knight or faking his death, all of the Robins were much needed by Batman.
So do you agree?