William Yorick was a blast to play, and I recently won a two-player Dunwich Legacy campaign with Daisy Walker so here are some observations for people considering our favorite actor-turned-gravedigger. This will be a slightly biased review towards multiplayer implications, as I exclusively play in 2-player or 4-player games. Yorick has real issues with consistent clue-gathering (i.e. investigating when he doesn't have tricks up his sleeve), so I think he's a better fit in multiplayer anyways.
This is going long, so here's a TL:DR:
Pros: ability provides flexibility and value, the combination of guardian/survivor can provide great burst potential, good enough stats (in a purely bodyguard role).
Cons: not a consistent clue-gatherer. Resource economy is an issue. Card draw comes down to drawing Rabbit's Foot or using off-turns with nothing to kill (in a multiplayer game).
Now for the long version (you've been warned)
Front of the card: Yorick has fine stats except for a lack of investigation; and a decent 'fighter/bodyguard/tank's healthy and sanity of 8/6. Whether you'd rather have 9 health and 5 sanity instead of the 8/6 split is up to you and your playstyle. His ability is incredibly impactful; letting you replay assets from your discard pile when you kill enemies. This gives him tremendous flexibility to meet different challenges any given scenario can present. At 0XP; this lets you recur Leather Coat and Cherished Keepsake for defense, First Aid for healing/support. Gravedigger's Shovel gives him guaranteed spot clue-gathering, Baseball Bat can be recurred after an unfortunate chaos bag pull. Lantern is an option, but I'm not sure if it's a great one (-1 shroud isn't great, and Yorick is well set up for dealing damage). Later in a campaign, you have access to Police Badge for bursty turns. Key of Ys because... it's the Key of Ys. Yorick's ability even synergizes with the Key's penalty of making you discard 10 cards off the top of your deck if it goes away. If you aren't satisfied with Teddy bears to protect your sanity, Elder Sign Amulet is a reasonable choice, especially at a resource cost of 2 and XP cost of 3. The only downsides of the ESA are that Cherished Keepsake is free (and it turns out saving resources is really important for late-game Yorick), and Police Badge takes up an accessory slot.
And that doesn't even cover allies. You can go in many different good directions with allies with Yorick. The upgraded Aquinnah can act as his 'boss-killer', along with the combination of baseball bat + Will to Survive. Baseball Bat + Will to survive + Police badge can deal 10 damage in a turn! Brother Xavier is a great sanity soaker and chaos bag-free damage source. Both Beat Cop varieties are reasonable choices. Charisma can be a great way to go with him.
Elder sign effect: +2 and if you win you get to return a card from your discard pile to your hand: +2 is nothing to complain about, and the bonus is great for grabbing Emergency Cache, which you're going to need to keep using his ability to the fullest.
Back of the card: Guardian 0-2 gives him access to great allies as previously mentioned. You don't get access to the best guardian weapons, but Yorick has alternate boss killing options at hand. Shotgun and Lightning Gun aside, you still have a great assortment of weapons. Both .45s, Machete, shovel, and baseball bat do work, and Yorick won't have to settle for inferior options like knives or kukris. Of course, Survivor 0-5 has benefits. Lucky!, "Look what I found!" (although his low investigate skill means he can easily fall below the requirements), Will to Survive is one of the best 'clutch' cards available. And for later scenarios Survivor brings some high-powered Exile cards such as Flare, Devil's Luck to help prevent backbreaking hits to health or sanity, and A Test of Will as a form of a Ward of Protection.
Signature cards: Another place where Yorick shines. Bury Them Deep removes an enemy from the encounter deck. This is handy in several scenarios to remove a particularly annoying baddie. And extra XP are always welcome. His weakness Graveyard Ghouls is not that big of a deal; usually just another enemy to add to the pile. There are worst-case scenarios to draw it, but you can say that about most weaknesses. As long as you have a weapon out, and especially with a good ally or two, the Ghouls are very manageable.
Mulligan strategy: It's very important for him to start with a weapon, so mulliganing events (minus emergency cache, probably) and skill cards for weapons is advised. Having an ally in your opening hand is an important secondary goal. It's hard to overstate just how good Leather Coats/Cherished Keepsakes are for him; if I have a weapon in my starting hand it's a good idea to mulligan for those.
I've already gushed about his strengths, so now I'll talk about weaknesses. As previously mentioned, he's no investigator. He can dig up the odd clue or two in a pinch, but it's night and day compared to a dedicated cluver, or even most 'generalist' investigators like Rogues and Wendy Adams with Lockpicks or Mystics with Rite of Seeking. So as a solo, probably not a good choice. But in a multiplayer campaign, his biggest weakness is his resource economy. His allies and assets aren't cheap, unless you want to run with Peter Sylvestre and/or Stray Cat. Madame Labranche as a secondary charisma ally may be a consideration; I wouldn't want her over a beat cop however. A real plan b (or plan a) for allies would be to save up for The Red-Gloved Man. You could kill something and play Red Gloved Man from the discard pile to boost investigate for some sneaky weakness mitigation. Graveyard shovel and Baseball Bat aren't expensive, but replaying them can be. In multiplayer, if you're not killing something, you're often going to be trading actions for resources, instead of helping to gather clues and advancing the act deck.
You have limited card draw as well; it's just Rabbit's Foot and Prepared for the Worst. This means Yorick isn't well-equipped for poor opening draws. I found this out the hard way, mulliganing 5 cards without finding an ally nor a weapon during one scenario. It's really important in this game to get set up in the opening turn of a scenario.
In conclusion; Yorick is well-positioned in a specialist role for a 2-4 player group. You can cover for his weak investigate potential much better in that setting. Turns out the combination of guardian/survivor is incredibly good for fighting. His ability really elevates specific disposable cards, and is one of the better abilities in the game IMO. For people who want to play the monster killer/bodyguard role but want something a little different than a Guardian, Yorick is both fun and effective.