So before anyone nuke this thread saying that any encounter with 4+ mobs should be assassination, I'm well aware of the performance disparity. What I am however interested in, is how people deal with add situations as combat. Some questions for debate:
At what add count do you replace SS with FoK as CP builder?
At what add count do you turn off BF for more FoKs - if at all?
When using FoK, how do you prioritize SnD and CT uptime?
Last time I checked, according to EJ, using FOK is/was indeed worth using at SOME point, but the amount of enemies required was (and probably still is) apparently uncertain - Needless to say, it's some unrealistically high amount of adds; numbers which you're unlikely to find in any raid environment.
To break down your questions:
1. Uncertain.
2. No idea, really. Haven't seen it discussed.
3. SND is always your first priority as Combat, no matter the situation. Your energy generation is directly linked to SND uptime; any lost uptime results in diminished output.
2-3 targets: Single target rotation, ruptureless, with blade flurry
4-5 targets: as above, but I replace eviscerate with crimson tempest, I don't bother with FoK
6+ targets: full AoE rotation (Fok + CT)
Whether or not it's optimal, I do not know. The reason why during that intermediate count that I use CT in place of eviscerate is because at ~4 targets, CT will do similar or more damage than eviscerate x 2. However, since FoK does not advance BG, I do not know how many targets you need for it to be worth stopping a single target rotation, this probably depends more than anything, on the duration of the pull once there are many targets.