I’ve had a lot of people ask me what the “Best-in-Slot” trinket configuration is. And to be honest, that depends. One trinket is clear: Variable Pulse Lightning Capacitor. Whether heroic or non-heroic, this trinket will be BiS for you.
The second trinket is a bit iffy. Generally, the heroic Necromantic Focus will be your second trinket, unless the DMC: Volcano will put you at or above 2637 haste, which is a DoT breakpoint.
Now, if heroic Necromantic Focus is not available to you, DMC: Volcano will be your BiS option, UNLESS it’s a heavy solar cleave fight with mushrooms (See: Rhyolith and Ragnaros). If it’s one of those fights, you will want the normal Necromantic Focus for the mastery and Eclipse damage.
Confusing enough yet?