Seriously, read the ToS.
A tank being petty and not doing the job they queued up for and intentionally letting people die is not "difference in playstyle" and it has its own section in the ToS.Obstructing Gameplay Using Combat
Refers to an act of obstructive behaviour such as using specific skills in an unintended manner or taking advantage of battle mechanics to interfere with the gameplay of other players.
Key Points
It is prohibited to interfere with the combat of others in the following manner:
Using actions during combat to cause other players to fall from platforms or field areas to incapacitate them.
Using and manipulating enmity-related actions in an effort to incapacitate other players or interfere with gameplay.
Gathering groups of enemies to obstruct the view of others.
Me telling the healer to DPS and the healer answering "I only heal" is, on the other hand, a difference in playstyle. And you can't kick someone for it.