Many, but not all, of the older raid bosses were adjusted (either in their power, or the mechanics of the fight) to make them soloable. Not all of them.
And "soloable" does not mean "faceroll". It means they can be done with a powerful enough 90 and good use of the character's abilities and good gameplay/tactics/handling the fight mechanics.
^This, soloing isn't supposed to be easy, it's a challenge (depending of the raid of course), you do it for fun, not for gear nor progression.
The nerfs implemented were supposed to made some fights more solo friendly, i.e mechanics in wich you had to have at least two players or the boss despawns, damage, health and other factors are and must remain being the same.
Not true....they nerfed damage already......the first boss in BWL takes less damage from the blackrock mobs