All right, in the bankai I have removed the possibility for multiple, simultaneous, ranged attacks. (Other than the spit which is a desperation move and just makes me chuckle.) And the possibility does not exist at all in shikai. I have also made it clear that staunch defences will not instantly fail against either the bankai or shikai and quantified it a bit more to a level that I believe is fair. I have scaled back the range of the attack in both bankai and shikai and cut down the length of time the metal exists when separate from the blade in bankai. 

As it stands I do believe everything is fair and balanced. When comparing it to the other captains I believe Akimoto stands a chance because of his regenerating health. The flying metal (in my head) will burn his flesh away about as quickly as it heals up, leading to a stalemate unless he gets hit in something particularly vital and weak like the eye or the neck. Only the contact with the sword itself is really going to be able to hurt him faster than he can heal which is fair because otherwise he can’t be hurt at all.

The comparison with Yue is a tad harder because it is asymmetrical. But I believe it to be balanced. Her one hit nerve dulling dooms anyone it touches as they will not be able to effectively run or parry so the follow up strike could readily kill. As for the lightning, even at 20% below natural lightning strength and speeds and assuming normal lightning rather than unusually strong lightning, it will be traveling at 2960 miles per second and imparting 400 mega-joules of energy with a core temperature of 40000 kelvin which is several times hotter than the surface of the sun. That’s just comparing shikai, bankai comparison is a similar exercise but with numerous varying abilities the comparison becomes really clunky. Plus it gets even clunkier when you start trying to work out just how fast shunpo is and how small reaction times are to function at those speeds and the whole things becomes impossible to accurately compare so with Yue it’s a rough comparison at best.

As for how anyone else can deal with Osamu your best bet is to kido him into the ground, just back away and take as many shots and throw as many spells as you can. Beyond 30 meters even at bankai he is useless.