I'd like to start up a discussion on Delirium, Blood Weapon, and Blood Price. I feel that these abilities are less well understood than Bloodspiller and TBN, which significantly more analysis has gone into.
I'm going to mainly focus on single target. As of patch 4.05, 1 DA (2400 MP) is worth 168 potency under Darkside, and 50 blood is worth 165 potency under Darkside with no Grit.
Blood Weapon
Blood Weapon is functionally analogous to FoF and Berserk. The difference is that your actions during the window are converted into MP and blood, which then have to be converted into potency. As with other windows, you want 100% uptime when BW is active to avoid losing additional potency.
Blood Weapon has 3 effects:
1) Reduces auto-attack delay
2) Reduces GCD length
3) Gives 480 MP (0.2 DA) and 3 blood per tick (each tick is worth about 44 potency).
The standard greatsword delay is 2.96s. Under BW, this is 2.66. You gain an extra auto-attack for every 27 seconds of BW uptime.
There are 5 auto attacks in the window, netting 2400 MP and 15 blood.
There are 6-7 GCDs present in the window, netting 2880-3360 MP and 18-21 blood. The cut-off point for the 7th GCD looks to be around 2.38s (2.14 under blood weapon). This works out to be a 67 potency gain/minute. Because Blood Price ticks do not occur when spells are used, any non-weaponskill GCD used in this window is a 44 potency loss.
Overall, you gain about 5760 MP and 36 blood, for a total of 528 potency. Fitting in C+S or Plunge into the window nets you an additional 44 potency each.
As a comparison, FoF gives you about 855 additional potency every minute, while BW gives you 792 (880 if you correctly align your oGCDs in the window, which isn't always possible due to the fact that BW is on a 40s recast, while Plunge and C+S are on 30 and 60s recasts, respectively).
One caveat to this is that BW ends when you activate Grit (imagine if FoF turned off if you switched into ShO). So you're effectively unable to change stance until the window ends (i.e. for 38% of your total uptime).
Another point worth noting is that, when you factor in the gain from Syphon Strike in the window, you gain about 7560 MP. That's about 80% of your MP over two combos. As a result, if you use it immediately on pull, you'll hit cap. You'll want to delay it slightly to align it with your opening burst, giving you some time to drive your MP down and open up some room.
Blood Price
Blood Price is tuned for multiple targets. It restores 120 MP per attack received (0.05 DA) and 1 blood. Each tick is worth 11 potency.
It also gives 4 blood every 3 seconds, regardless of whether you're being hit, as long as there is an active mob present (i.e. it can generate blood while you're sitting around waiting for the boss to do the big wind-up animation for their special move.) This gives you an additional 20 blood (66 potency). You need to be hit roughly 3 times every second to have an equivalent potency gain to Blood Weapon.
Delirium
Delirium gives you 1 DA worth of MP and extends BW by 8 seconds. There are 3 auto attacks and 2-3 GCDs here, netting 2400-2880 MP and 15-18 blood (264 potency). If you execute it correctly, you gain 267 potency (for a total of 789 potency). If you don't, you gain 3 potency instead. It also commits you to staying out of Grit for the next 23 seconds.
If you choose to use Delirium on Blood Price, it gives you a 16 second extension. This gives you a total of 40 guaranteed blood (132 potency). You now need to be hit about 4 times per second to break even with the Delirium-BW window. This is unlikely to happen in single target. You're also committed to stay in Grit for the next 30 seconds.
The new Quietus is interesting. It has a built in BW effect, giving you 480 MP (0.2 DA) per mob. I'm not really sure what the trade-offs are between Quietus, Delirium-BW, and Delirium-BP are, but I suspect that you're probably going to prefer to spend resources on Quietus over the other two. So I'm not really sure what role Delirium-BP has at all.
Thoughts?