To get a 100% pandemic refreshed garrote. That garrote ticks for so much damage it's crazy. If I refresh it 10 seconds after casting, that means my garrote dot is at ~5 seconds remaining, I throw another 13-15 seconds onto it and it refreshes at the 125% increased damage level. For some reason I want to say when I do this ingame my weak auras tell me I have around 23 seconds of buffed garrote, at 240k per tick, that's pretty solid.
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Also, I double checked in discord to see what they're recommending for openers with subterfuge and 4 piece. They actually linked me the exact opener I put in my above post. But we came to that openers conclusion on the blizzard rogue forums.