Guessing someone watched sco's video and incorrectly believes warriors are bad for tomb.All tanks are viable for either heroic or mythic thats all that can be said, are a few tanks more gimmicky? sure but the balance is realy close. what type of tank you are using is mostly the least problem when progressing tbh (exception of Krosus maybe) on a side note unless you play in top 50 you should never worry about your tank class not being viable and you should just play what you enjoy the most.
Tank balance is a LOT better now, for sure. There's still 2 tanks where you're better off rerolling to your 20ilvl lower alt though.