Hi Hardmode EC healer here, and Shadow Tanks are the hardest to heal, juggs take significantly less damage then shadow tanks do. The reason shadow tanks are the best right now is due to the higher threat ceiling allowing dps to do their job without pulling aggro and killing the raid. This was rightfully fixed this patch.
As for pvp no one ever complained about a Tank being hard to kill in pvp, people complained about tanks in dps gear putting up competitive numbers while gaining significantly increased survivability. Instead of fixing the problem, dps, they pulled a Dick Cheney and nerfed tanking.
After the healer changes and now this I'm fairly certain bioware class devs are incompetent.