I wouldn't say it's broken, but a hill dwarven bladesinger (now ok with Tasha's) is pretty potent.
One of a bladesinger's biggest weaknesses is HP and a hill dwarf gets a bonus to Con AND a bonus to HP. With the floating stat bumps allowed by Tasha's they can still have a top INT too. Even if a player chooses to not push Con (say using the floating bonus for Dex and Int instead) they still have more HP than a typical bladesinger.
One of a bladesinger's biggest weaknesses is HP and a hill dwarf gets a bonus to Con AND a bonus to HP. With the floating stat bumps allowed by Tasha's they can still have a top INT too. Even if a player chooses to not push Con (say using the floating bonus for Dex and Int instead) they still have more HP than a typical bladesinger.