There are so many things wrong with this sentence, dude.
First, you listed off nothing but BatFamily characters. None of them have ever had to completely stand on their own. Second, one of them has
never made it on her own. (Huntress, her one and only ongoing lasting less than two years back when that
wasn't almost expected) Third, all the others, save Nightwing, struggle to sell on their own today. Fourth, all of these characters, save Damian, were created before the turn of the century in a very different market. And fifth, none of those characters were the first to hold their mantles and/or have books with them. Dick created Robin, wasn't the first Nightwing, but did have the first Nightwing ongoing. Jason was a legacy hero as Robin and the third or fourth character to call themselves 'Red Hood.' Damian's the 5th Robin, the blood Son of Batman and the previous Robin's ongoing lasted for almost two decades. Helena was the second Huntress. And Barbara? Not the first Batgirl, the last of the 3 'real' Batgirls to get an ongoing (her current one being by far the lowest selling Batgirl ongoing ever) and her non-legacy identity was stripped away from her.
NAoH books are set in the main DCU.
Not gonna bother with another full breakdown here. This just isn't true.
March 2018 Diamond Sales
Sideways #2: 23,807
Damage #3: 22,394
Silencer #3: 18,208
I don't count Teriffics as those aren't new characters and the rest don't have sales data out yet.