I personally think almost all achievements should be account wide... Its not the character that earned the achievements, its indeed the player... bc trust me, I AM THE ONE THAT PLAYED FOR 6 years not a character.
And someone once mentioned " how will i know a player is good bc now their alts have all these good achievements.. how do i know this dude is good on his alt?" HELLo HOW ABOUT DOING IT THE OLD FASHION WAY, test run him, talk to him, ect... you know, what u did b4 there was achievements in the game.. sheesh.
Im sorry but If i spend 2 years grinding out Battlemaster and mounts/ titles ect... heck ya I wanna show it on whatever character i play., bc no my mage didnt earn it I DID!.
And if for some reason my guild no longer needs my mage and they need a healer... I roll a healer, then yes i should have the same achievements show on my healer bc i as a player earned them.