Scharn is a prem, both are BB's.
A rather good case can be made that BOTH are OP.
Atlanta is a cruiser, and is EXATLY where it belongs.
Your entire argument is that because 2 BB's are at tier 7, Alaska should be tier 6.
What has one got to do with the other?
Alaska isn't a battleship, it is a cruiser.
If you put her at tier 6, her AA will be nerfed to crap.
her secondaries will be nerfed to crap.
Why do you want to put the best USN CA in a tier where she HAS to be nerfed?
LEAVE ALASKA A CRUISER!!
CB Alaska as a T8 cruiser would be fine with me, but as battlecruiser (Hood, Renown, and Kongo)....ouch. Depends on how WG defines her.