How Can I Play Like This?

[Culfinrandir]

It's still third party. They can't ban some then not ban others for breaching the same rule. Fair or not, cheating or performance monitoring. I'm not against a dps meter, but if it's allowed then it should be placed in game.

There's no ban on third party software, only third party software that modifies the game or the data stream. Otherwise they could say that using Chrome to access information about game play is "using third party software". Not all DPS meters fall J to the banned category.