[Executor]

While giving blood boosters to B1 hunters sound like a good option when no SDR are present I see two problems;

1. Blood hunters would get rather vulnerable in open provinces, the fact remains you pull more gold from forts due to administration so open provinces are generally a better option to blood hunt, and I for one would target those provinces first for assassinations, remote spells and attacks. So you'd need forts or something in blood hunting provinces to protect your investment. We all know that it sometimes takes only one turn of war to halt or cripple a blood economy.

2. Every blood hunter will have to take about 4 turns at least to pay his items off before he starts hunting, not to mention that you have to use your rare B2 mages to start the initial hunting and get the slaves for the boosters, since hunting with a B1 mage is ineffective.
Also, rather than forging items, I'd much prefer empowering to B2 myself, after all it's only a 5 slave difference without the hammers.

I of course see no way around this since I think Vanheim is screwed regarding blood hunting personally.

Vampires Lords would blood hunt good, but using them for hunting means you're not using them to summon vampires, which is wasteful to me.

In regards to blood hunting power levels, I'd say around 7 blood hunting provinces is average.

Blood hunting under taxes is a bad idea too, regardless of patrolers, or scales for that matter. The only time I see this pay off is when you have a gold mine in a province so you can stack up the taxes and blood hunt.
Growth scales are usually meaningless in blood hunting provinces. The more pop you have they more you'll get and since blood hunting provinces tend to have 4000-7000 population usually the growth will be marginal. If you hunt, tax and patrol you'll kill that provicnes blood hunting abilities rather fast I feel. It's rather easy to lose 500 pop after a good blood hunting turn.

As for the fountain of blood, I have yet to see anyone use it for blood hunting.
You take it when you have a blood nation (is it restricted to blood nations only?), at which point having your pretender blood hunt isn't all that of a bonus, especially since you'd have to teleport him away as blood hunting in your cap is a fast way to drive your pop down, the more population there is, the faster they'll die, so you need to have either air or astral, to research teleporting, and build a second fort for the pretender if you don't take astral for returning. A hassle I think.

Oh, and as for summons, I'd go for ritual of 5 gates mostly. Summon some Ice devils or Heliopagi that can cast ritual of five gates in time of peace with some boosters (use them as SCs when you need to). Massing only storm demons can be countered easily with the right stuff, and it takes a lot of mages time summoning them one by one.