Really? I don't play TTT2 but I see it played all the time at the local arcade and it seems like I always see the same 6 characters or so. Especially the dude with the mechanical arm.
Character popularity doesn't necessarily imply that that character is top tier.
But really, TTT2's balance is fantastic. For a game with 50+ fighting styles in it, almost everyone has the tools they need to compete. At most maybe 3-4 characters are unviable, and one of them (Dr.B) is very obviously designed as a joke character anyway. The only characters that stand out as noticeably better than everyone else are the Mishimas, and that's because of their EWGF (which is frustratingly hard to sidewalk now). However, they each have their own flaws (half-baked mid pokes, risky lows, poor tech crouch/jump ability etc.) that stop them from being over-the-top good.
But Injustice is a totally different kettle of fish, and all things considered, since they were obviously trying to make each character play as unique as possible (unlike the Tekken series where most characters have broadly similar strategies), they did a decent job. Making it so that all 30 characters are viable when they all have such conflicting fighting styles is... not necessarily
impossible, but extremely fucking difficult,
especially when it's a brand new fighting game which doesn't have any prequels to build off of (the Tekken series has basically been building on top of Tekken 3's engine for a decade and a half now, so has had a lot of time to refine the balance) In such an event that balancing a character is an insurmountable task (i.e. they're either going to be overpowered or underpowered, and getting the middle ground is not practically possible), opting for them to be underpowered is
always the better option. To provide a (highly) simplistic example - if you have 25 solid characters, and 5 crappy ones, those 25 characters will be viable (and 25 viable characters out of 30 is a great success rate for a fighting game). However, if you have 5
overpowered characters, then at worst,
only those 5 overpowered characters will be viable (5 out of 30 is a very poor success rate).
With all of that in mind, I have to congratulate NRS on reaching a reasonable compromise on the game's balance. The Tekken series took 14 years to do that. The Street Fighter series took 19 years to do that. Mortal Kombat
still hasn't done it after 19 years. NRS did it on their
very first installment, with only a few months' worth of patching.
And this is why, although certain individual properties of moves annoy me like fuck, I can't come down too hard on them, simply because they did a solid job with the resources available to them.