I'm sure it wasn't easy, but really, Big Daddy? I had to look at the list to remember the nobody cast. The Infamous guy? Killzone guy? Dead Space guy? Starhawk guy?! These are deep, deep fucking cuts. I think their logic was popular game = popular character, prioritizing that over actually visually interesting characters.
It looks like Dart was planned as DLC (RIP), meaning they had the rights to him but prioritized a bunch of generic soldier type characters over him. Same with Kat. I'm sure there was just some good old fashioned mismanagement and bad decisions at play too.
Take it in context of the time period as we are talking 2012 here. Much of the roster was a solid representation of Sony during the 2-3 era and many choices were made off representing the IPs going at the time.
Gravity Rush only came out a few months prior to the game, so who knows how well informed the team was on it. This was an American team, making a game simultaneously to that of a Japanese studio.
Infamous was a major PS3 IP. Cole was more interesting in concept than final game as there was not supposed to be 2 Coles. There would be a good/evil mechanic that would make him a more interesting fighter and more inline with his game, but it was scrapped for being too ambitious to pull off.
Radec was the only character from Killzone that anyone cared about. His play style added a zoner to the roster as he was a sniper type. Killzone was also an ongoing IP even into the PS4, so I doubt they couldn’t include it.
Sony seemingly became more involved with DLC, leading to many marketing picks. Ironically, Kat was likely a marketing mandate alongside StarHawk and Dead Space. The team wanted Dart, but DLC didn’t sell enough for Sony to finance. Also, before someone says gotcha to Sony’s lame picks, the actual reason it didn’t sell was because they made it free for a brief period for some idiotic reason.
PS All-Stars was the game that never was. It was a great representation of the PS2-3 era, but nothing more. Honestly feel bad for the team as everything was working against them, yet they clearly had a passion for the project.