Blizzard has posted a clarification on the philosophy behind the Tank and Healer trinket change.
Assuming a tank trinket has 100% of its budget allocated to damage effects, a tank could expect it to deal equivalent damage to a DPS trinket for them. DPS players would therefore deal ~33% less damage by equipping the tank trinket instead of one intended for their role.
In general, the trinket decision for tanks should feel more along the lines of “deal 100 damage
and gain a defensive benefit” with an offensively-oriented tank trinket (or a more defensive option as needed), or “deal 100 damage” with a DPS trinket.
This seems to be a very confusingly worded Blue Post. I believe what this is trying to explain is that a Tank wearing a DPS trinket should now deal the equivalent amount of damage as a Tank-specific offensive trinket, but they will also gain a defensive benefit from wearing the Tank version.
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