Jann Lee, Lei Fang and Gen Fu are all extremely linear and that didn't stop them being top tier. (I say didn't as I haven't Crippled is a very strong word for a character as good as Kokoro. She is still able to by pass the stun game easily, her damage output is still extremely high, she's still really safe. If linearity is such a problem post patch then Jann, Lei and Fu are fucked too, and I don't see that being the case.
Jann Lee's linearity is highly exaggerated in this community. He's one of the characters that has circular attacks at all heights, and can use them without any prior move in a string. And one of his mid tracking moves can even cause a limbo stun. I would not consider Jann Lee that linear at all. He has more than enough proper circular moves to deal with sidestepping opponents. Where this popular delusion came from that Jann Lee is very linear is beyond me. It seems people believe it to be true just by repetition. You don't need a whole plethora of tracking moves to deal with side steppers. If you have two while at least one is a stand-alone mid, you're already set. Not to mention he has OHs and stuff.
Leifang is more linear than Jann Lee. She only has high tracking moves that can be used on the fly. Her mid tracking moves are all moves during strings. So she has to guess a lot between someone sidestepping or someone doing a crushing move or low when attacking since the prior moves are high. Her only low tracking move is from 4KKK and its variants, of which the final K is a crappy move. Jann Lee does not have that issue because he has immediate mid trackers.
Gen Fu is also more linear than Jann Lee, and more linear than Lei-fang. However, he has the advantage that his main tracking moves are low. With his parries, people will not be attacking mid a lot, so he is more free to use his 1P to track sidestepping opponents. Even highs are hard to attack him with, since he can easily crush them with multiple moves. Gen Fu is top tier because even though he's linear, he's easy to use and easily gets great stuns in with his fast mid P, or his crushing moves, and most importantly, he himself is very hard to stun due to his parry and crushes.
Kokoro has an i10 jab and an i12 mid punch, with that she can compete with every character in the game speed wise. I'd kill for an i10 jab, just so I had one attack that could beat an i11 mid punch.
She might have an i10 jab and an i12 mid punch, but that speed alone does not make up for her inability to defend herself. How many times are you actually at a certain advantage or disadvantage, that the best option is an i10 jab? That's probably only at the start of the match, and you don't want to start attacking with your i10 jab to outdo any character that's as fast or faster, because the risk of being crushed or hit in the face is too high. Most of the time you'll be at a certain disadvantage where an i10 jab would lose anyway, or you're at an advantage where 13i stuff will beat out the opponent. You don't really need an i10 jab when you can crush mids with your character. Otherwise, just learn to bait the mid punch and hold it.
Kokoro is not in the same league as the three characters above. This seems to be another thing that people seem to believe due to repetition, probably due to early reports saying she's a monster or something. She does not have the movement and spacing speed of Jann Lee. She does not have the ability to crush like Gen Fu. She does not have parries like Leifang. She lacks OH which Jann Lee and Leifang have, her few circular attacks are high while all three of them have better options, she lacks proper low crushes which all three of them have. She's basically a purely offensive character with a very crappy defense. And above all that, she's the most linear character in the game (along with Akira). Not only will she have trouble regaining momentum after getting hit once, it's fairly easy to stop her in her tracks before she lands a stun in, if you know how.
As in all prior games, Kokoro's lows suck. She definitely needed the 6P+K buff in v1.03. Aside from that move (which lacks the stun in v1.02), she has two main things to break through people's defenses while attacking, which are the mid string grabs, and her unshu stance. The mid string grabs become predictable if used too much and the follow-ups can all be held, so it's a guess two times in a row, just to get a stun in. Her unshu stance is the same story. It can be interrupted easily since it doesn't do shit other than look flashy, and even then, all the follow-ups can be sidestepped, held/parried or even fuzzy guarded. These are the only two moves that reliably give you advantage, without resorting to snail speed attacks like P+K and 214P. These strings that allow her to go into her grabs and unshu stance have to be mixed in with her normal attack strings to have any sort of effect too. Without using those two options, you just have to hope the opponent stops blocking at the wrong time so you can hit them with something. Before that happens, you've probably already been sidestepped and counter attacked, and with the lack of moves that crush, you're in trouble.
Despite her great tools when she lands something, getting inside your opponent is the tricky part with her, and her crappy defense and linearity makes her very vulnerable while trying to do that. It definitely makes her at least one tier lower than the three above. You have to mix up quite a bit to land something. The good thing is that when you do, the mix-up requirement when the opponent is in stun becomes minimal since she launches and bursts easily, and her damage is respectable in those cases.
And that's without taking the bad matchups into account. Or maybe I simply don't know how to play DOA5 Kokoro...
Honestly I don't think people can be completely objective about their characters, I mean Jann Lee players still deny him ever being top tier and say he is mid tier at best. Perhaps I'm the same way with Helena I dunno.
Yeah. People love to inflate their egos, and pretending that their characters are worse than they actually are is a nice way for them to do that.