Even if I feel the three tanks are not equivalent, the DRK is the one who has the perfect spell for Tank Buster, it's called TBN.
And since he can put this TBN on him, or on any player in the party, it makes it better than the WAR to protect the team, even if the WAR can make more dmgs.
Intervention/Sheltron are the same thing, arguably better. Sheltron is approx ~24% damage down on PLD (compare to TBN's -20% on DRK), and Intervention is -10~40% on a party member (compare to TBN's 10%).