Back to the filthy casual corner with you! /s
Thereās a difference between failing to define a game, and purposefully leaving it undefined. When Gearbox creates a new IP, they create a new genre.
Computer says no. Borderlands was a lucky coincidence. Battleborn looks interesting but is hardly a new genre.
So what other game is the same genre as battleborn?
I wouldnāt feed the trolls, dude.
Just because I donāt agree with him doesnāt make him a troll. Its also in the rules that we talk about the game/topic and not each other.
As someone who utterly hates math with passion thanks to a horrific math incident in my preteen years, I couldnāt care less about the numbers. Just the fact that I know there is variation appeals to me, regardless of how big the scary scary numbers are.
I think the point is that while the math is sound, it doesnāt really reflect what will happen as we play. There are going to be some combinations that wonāt work well in terms of ability choices and team compositions. Teams will likely want support capable classes to make support builds that limit a lot of the choices. And a lot of people will choose one character and stick with it. Even if they play multiple characters, most of them wonāt be explored in-depth, the majority of players will pick a main and develop it, get to know itās permutations much more than the rest.
Even so, I do think there will be plenty of room to explore for those of us that like to do that. Others will follow builds made by players with a bit more expertise (hopefully) and thatās fine, too. Iām really not worried about this at all; the actual possibilities may be far less than the numbers in the trailers, but āfar lessā in terms of those kinds of numbers still leaves a lot of possibilities! 
Iām a solo-oriented player myself and so having solo play is important to me. But one thing I know from raiding in WoW, there is a sense of team accomplishment and camaraderie that canāt be had in solo play, and I encourage all gamers to give group play a go. Of course it works best if you find like-minded players to team with.
I certainly donāt get the idea that solo play is āgrafted onā for Battleborn. Borderlands was advertised as a co-op game that you could also play solo. Despite its co-op focus, it was a great solo experience (for me anyway). Gearbox has proven to me that they understand solo play, and a lot of the team leading the development of Battleborn worked on Borderlands. Iām very confident Battleborn will give me a good solo experience.
Iām also pretty confident that there will be more class build possibilities than Iāll ever fully explore. I might develop one or two classes to a high degree, but most of them - no. We might be talking thousands of possibilities instead of the huge number calculated in the trailer, but thousands is a lot of variation. And it really wonāt be like the gun drops, because you donāt have to wait for RNG to drop you a legendary instead of a common. Itās more like all the abilities are legendaries, and you pick the ones that work best for you. Thatās the way I look at it anyway. 
So⦠donāt play then? I donāt see what the issue is. When I donāt like something, I donāt waste my time coming to forums for it talking down unless Iāve A) invested money or B) invested time. Chances are youāve done neither. Thereās thousands of other games at your disposal to choose from, Iād recommend checking them out.