Don’t you need to graduate the student sometimes? At Disgruntlement 5 you get an auto-fire card that costs you stuff, says the wiki. I would guess that dealing with that cost is pretty bad for your EPA especially since you have to fish for the right cards.
So, here’s what I think the math is for Cartographer’s Hoard, with Haphaesta at Watchful 291 at a Lab Level of 7 (my stats).
First, figuring out what’s the research-per-action of using Haphaesta to work with a Visionary Student. It looks to me like the Visionary Student has a 50% chance of being advanced at each step (or becoming disgruntled), so:
1 action to hire the student.
At level 1-2, there’s a Broad (210) watchful challenge, which has an 83% chance of success at Watchful 291. It gives 4+7 = 11 research on success and one less on failure. So on average, it takes (2/0.5/0.83 = 4.81) actions, and gives (2/0.5/0.83)*(10+0.83)=52.19 research.
At level 3-4, there’s a Broad (215) watchful challenge, which has an 81% chance of success at that level, which gives (4+72=18) research on success, one more on an advancement success, and one less on failure. So on average it takes (2/0.4/0.81 = 4.93 actions) and gives ((2/0.5/0.81) * (18 + 0.810.5 - (1-0.81)) = 89.95 research.
At level 5, you switch to having Hephaesta supervise the student. This is a Broad (220) challenge, so is 79% chance at my level. You get 56/2=15 disgruntlements before the student needs to be retired - that’s the point at which an autofire card starts appearing that costs you stuff. It on average will take (15/0.5/0.79 = 37.97) actions to do this. Each action gives (12+72=26) research on a success, and (10+72=24) on a failure, so the average total research of this section is ((15/0.5/0.79)(24 + 0.79*2) = 971.39)
Then it takes one action to graduate the student. So, an average of (971.39 + 89.95 + 52.19)/(1+4.81+4.93+37.97+1) = 22.4 research per action.
As a bonus, this gives one 2.5 echo item for graduating the student so an extra 0.05 EPA :) and an unsellable rumor of the upper river.
OK, so using this method, the 2700 research for a cartographical hoard takes 120.5 actions (and as an aside, generates 6.05 echoes of Broken Giant from graduating students) and, taking account the 2 actions to start/end the research, and 2 actions to enter/leave lab, gives a final value of 2.56 EPA, going through a bit over 2 students per Hoard.
Various tweaks to this EPA: if you leave the lab and come back twice and count those actions, EPA is 2.48.
If your Equipment is 8 (Fate), your EPA is 2.75.
If you have Watchful 300, EPA is still 2.56.
If you have only Watchful 250, your EPA is still 2.54! So Watchful level really matters quite little for the Hoard.
That’s what I’m getting at least. There’s some guesses there at advancement and disgruntlement probabilities, it looks like 50% to me but I don’t have a big dataset.