True, but by default Nippon and Cathay are going to fight anyway without our prodding. There's some opportunity to make money or whatever there but it doesn't yet look worth the effort involved to do something serious until they beat each other up a bit. Hell, what we really probably want to do is trigger a conflict between the Ogres in the Mountains of Mourne and Cathay immediately to prevent whatever the hell is going on there from hitting us in the Dark Lands. I might be willing to accept a split focus to spend a couple Authority just on that while our main military operation is going on elsewhere.
As for Karaz Ankor, yeah, the main thing is that we want to approach this from the standpoint of: what are we expending for what gain, and does that tradeoff make sense compared to other options on the board? So, how do we evaluate Karaz Ankor? We know they already had their exodus, so what's remaining now is a bunch of diehard prepared defenders with far less treasure than used to be there that's probably either super sealed up or booby trapped for whatever they couldn't carry off when they left. This seems to be like the definition of a hard target with little payoff, which is ideal for sending someone else in to die on and sweeping in only later.
As for taking out enemies faster, we want to do so to the ones who no one else is going to hit in the meantime. Most of the other factions are going to weaken themselves naturally in the upcoming fight, but no one's going to be looking at Nagash, for example.
Actually, here's a thought: If there's anything at all valuable in Kislev, we may want to hit them ASAP and steal it before Chaos rolls them over. Do Ice Witches have any appeal for us? Is there any special artifact Kislev has that we might want that wouldn't unduly weaken them in their upcoming against Chaos? Etc. Something to think about.
Agreed on secrecy, though.