Originally Posted by
Gaidax
Destruction guides are not properly maintained, half of the info there is flat out wrong such as M+ talents which is outright false big time.
The guy who maintains the Icy guide is a Warlock Discord admin, but he's a theorycrafting guy and certainly not a Destruction player. There is one thing you see in simulation and whole another thing in reality.
So no, don't use int gem, don't ever pick Soul Conduit and Inferno for anything (aside maybe Torghast, big maybe) and go to Warlock Discord Destruction channel for up to date info from players who actually play the spec and not just theorycrafting fanfic that holds no water in reality.
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As a quick cheat sheet - for raids a decent idea would be to go to WCL and see what top parsing Destros used per boss. Flip to HC and see what people use in top Destruction logs there you should get a decent "guide" out of that.
Mythic you won't find much info, because spec is almost dead for raiding with Affliction being vastly superior in pretty much every situation.