As of mod 12b a new signet was introduced. Once you completed a campaign, you can buy the signet and use it on one of your alternative toons. This will reduce the cost for that toon to complete the campaign.
As said, mains have to progress up to a certain point to be able to craft the signets. They do not have to actually complete the campaigns. The best example for this is the Cloaked Ascendancy, where you can get access to its Cloaked Ascendancy Signet of Patronage without completing most of the store and boon quests. All threshold tasks can be seen in the picture below. Going forwards signets will be available for all campaigns but the two most recent. At the start of the system that would technically rule out the Cloaked Ascendancy, but the devs included it anyway (yay!).
The basic idea of the costs is that you’ll gain roughly five times as much campaign currency from the signet as what it costs. It’s really not that hard to amass the necessary currency, it should take you about five days. Each signet however does also require 50,000 Astral Diamonds.
On alts that consume a signet a warning is displayed in case the character has already significantly progressed through a campaign. It’s a nice additional safeguard so you don’t accidentally use the signet on a toon that might not need it.
Sharandar fully profits from its Sharandar Signet of Patronage. All boons and progression tasks are cut in half, so your alts can progress with twice the speed. Granted, the campaign is already fairly easy to complete, but the signet certainly helps.
In Dread Ring we already run into a limitation of the system. Although progression quests are technically cut in half, they still require one Thayan Cipher. As said, everything is rounded up, and one divided by two, then rounded up, still equals one. So the campaign, with and without the signet, is taking you at least 16 days. For this one it would have been much better if the signet doubled the currency from the quests.
The rating for Icewind Dale is based on the assumption that reputation is correctly doubled. The dev blog clearly mentions that it should, but it wasn’t on the character I tested the signet on. So make sure to double check this before you begin questing with the Icewind Dale Signet of Patronage. Even if working correctly, the daily reputation quests are not as much of an issue. Right now you need 18 days of zerging three HEs and gathering 300 Black Ice, which isn’t that much work. The annoying grind comes from questing in the large Icewind Pass and Dwarven Valley zones to get Auril's Tears and Dwarf Gold. While the signet absolutely helps there in reducing the required amount, I would probably still buy myself out of the mess with Genie's Gifts.
It’s pretty much the same story for Underdark, which also fully profits from its Underdark Signet of Patronage. The thing that’s working against this campaign however is the fact that Faerzress is uncapped anyway and the progression task takes 18 hours to run. So in most cases you shouldn’t need the signet to be able to start the task each day.
Ding, ding, ding, we have a winner! I personally just don’t like the campaign setup of going out in the world and shoot a random mob. It’s dull. So reducing the grind to 16 days makes it worth it for me.
I was so hoping that the Patronage System would help in SKT, and it really does! The issue is that even with the Stormking's Thunder Signet of Patronage, it remains the most painful campaign to run both in terms of length and daily load. I’m pretty confident that I’d rather go with the full Storm King's Thunder Campaign Completionto dodge this crap, but admittedly the Patronage System majorly helps with Voninblod and Secrets of Ostoria farming. So this comes down to whether you think the 50% grind is acceptable. For me it’s still too much. I have spent enough hours with Module 10 and won’t ever come back.
It’s quite complete opposite for CA which is the second campaign to land a five star rating. All tasks in the campaign are reduced and no matter whether you want to go boons or dungeon first, you’ll get there twice as fast. The task cost reduction also makes more store tasks viable as you no longer spend more currency than you are able to safe with them.