I think the core problem is that we use the term "blanket siege" differently.
From my viewpoint, "blanket siege" does not automatically mean laying siege on the whole country. Covering two layers of provinces also count as a form of "blanket siege".
Higher siege attrition actually encourages this kind of "blanket siege", because the alternative, which is to use one or two large stacks to focus on a few target provinces, has become relatively expensive manpower-wise.
Oh, okay, I see what you're saying. If you're losing 1% regardless, you're incentivized to create 5 stacks of 5 rather than 1 stack of 30, since you lose the same amount either way. That makes sense.
This is why I suggested 'deeper' territory gives exponentially higher attrition, so that second layer would be losing 2% (or more), the third layer 5% (or more), and so on. Even better, the very act of walking that deep into enemy territory should see the standard terrain attrition also increase by the same amount, to discourage deep pushes into enemy territory without nearby allied territory.
I think this also points out another issue concerning the current risk/reward of wars and sieging. If I do have a 30 stack working on a siege, it should probably speed up the siege in some way. Right now, the only troop type that speeds up sieging at all are artillery. The risk (1% attrition) scales with army size, but the reward (siege speed) doesn't. I think the actual siege mechanics can be adjusted to make large stacks a bit more rewarding.
If you use a two-layer blanket scheme, you can still take over a medium country in 3-5 siege cycles or so.
This proves my point about the ticking war score. The current ticking war score is so slow that it is more efficient, and
optimal, for me to conduct total war and blanket the enemy, since the war score gain from systematic total war is faster and more rewarding than the ticking war score from the war goal. That's not a proper risk/reward curve. If the ticking war score were faster, at least, so that it was more time efficient than blanket sieging, then it might be worth it. But as you point out, its currently just easier to blanket siege and rack up higher warscore from total war tactics.
62 months is for the max 25% ticking warscore. If all you want is a single border province, then you do not need to wait for that long. 10% occupation warscore +10% ticking warscore + 5% battle warscore should be more than enough for a single province. If you want more, then naturally you have to wait longer.
But as you so eloquently said above, 3-5 siege cycles is generally shorter than waiting 62 months for a max warscore, and more rewarding in terms of warscore. Why wait 5 years for 25% when the game mechanics currently allow me to easily gain 100% in that same 5 years just by blanket siege?
It's not about 'just taking a single province'. It's about taking the 3 or 4 provinces on my border, and doing it in a way where I'm rewarded to play in a somewhat historical manner, focusing on border skirmishes and rewarding players for focusing on the wargoal itself, as opposed to kill enemy doomstack-split own doomstack-blanket siege.
Right now, the very mechanics of the game reward total war, so people like the OP naturally expect they should be able to earn more than just the 4 measly provinces on their border. What I'm ultimately suggesting is to create a system where you focus on those provinces on your border, and when that's all you can take due to war score anyway, you aren't scratching your head why you just had to conquer Iberia for them.
The real problem is that the
fastest, most efficient strategy is to to siege a whole country for what is considered a realistic/historical gain (of a couple provinces). You should be able to
optimally attain a border push through a border war, not total war. Unfortunately, that's not how the game works right now or how you're rewarded.
