Shizuha? Soft carry? Are we both misunderstanding something here or what? That shit is hard as fuck. And did we forget Tei or what?
What Rawr is saying, pretty much, is she's boring as fuck.
Ult isn't a team fight winner in any case if the other team has any clue of what they're doing. It's only people who walk into that shit and get cocky that die to it; even if other people derping is a reliable occurance, we can't call a skill useful if it's only useful when people screw up.
Tei is hard as fuck to gank because lol mines and 'hey I outdps you anyway with F'
Shizuha is hard as fuck to gank because of ult and entangle.
Reisen is hard as fuck to gank now because of LOL FREE WARDS WITH 1.5K CAST RANGE. (approx)
Koishi? Nope.
CONVERSELY, WHEN GANKING
Tei gets an auto stun orb walk, and possibly mines if he predicts your escape route
Shizuha gets her entangle
Reisen gets slow+god range
Koishi? Hope for crits.
If slows aren't legitimate disables, Ace, then why the fuck do we have Medicine as a ganker? Because when you gank, there's going to be someone else in the lane. And ideally they have a stun. If they do, Reisen lets you land that better. So does Shiz and Tei, for stun stacking. Koishi doesn't help you land your lane buddies stun at all, and in fact she may make it worse by scaring them off.
Reisen has a disable, Shizuha has a disable. Degrees don't matter, Koishi doesn't have either a soft or slow disable or an utility besides a-move. Koishi doesn't help her team at all beyond mana burn and dps. Reisen has slow, clones, free wards+snipe+aoe, doppelwalk, and range. Shizuha has a hard disable, +dps aura, potentially infinite absurd sustain, and a multi purpose ult. Conversely, Koishi has 'oh hey I get stronger when more people are around to disable me, so it doesn't matter', 'hi I have crit and eva but it doesn't matter because I can't stop you from just running away at all, via blink or w/e', 'ima mana burn one guy, everyone else nuke me', and 'hey guys whats going on'. She has the most dps in the kind of situation she doesn't want to be in. Not to mention Tei, who has impetus+stun as a normal skill, techie mines, and 'haha fuck your nukes' as an ult.
tl;dr the last paragraph: all the other ranged carries have flat damage bonuses that aren't based on god's luck
In terms of 'steroid', we're talking about flat bonuses Ace. Can't call crits a steroid when Reisen and Shizuha have a 'turn on for even more rape' button, a spammable one no less in Reisen's case, and Tei has a fsking orb walk.
Regardless of effectiveness, Koishi still has a crappy ass character concept. Reisen and Shizuha do contribute crap to team fights. So does Tei. And if your hero concept is 'right click all the time, and if you are having a hard time lose complete control of your character', that's fucked up in the first place. Hell, Koishi is helped by her team more than she helps her team. Reworks pls.
Your point about ranged carries lacking disables and not being able to contribute to team fights is hinging on your belief that 'Shizuha is a soft carry so she doesn't count' and 'slow isn't a real disable'. Not to mention you forgot Tei, who has a guarranteed fucking stun orb. On all three accounts, it doesn't work. All of the other ranged carries are suited to gank, Ace. Tei's purpose isn't to a-move towers. Why isn't Koishi?
Since you can't get it past your 'pick carry and win game' mindset, Ace, let me spell it out for you.
I don't disagree that Koishi can be strong, nor do I disagree that she can be really weak. Any team worth their salt would be keeping two nukers on Koishi's ass at all times. As far as I understand it, Koishi is a stupid hero, seperate from the 'good bad' axis. She's just...boring. And that's a bad thing.
Right now I treat Koishi like I do Maelstrom in DotA; the little kids get it because they want to look cool with minimum effort. The difference is that Koishi is a fsking character.