By now, all Daemon players are mostly aware that Flesh Hounds are one of, if not the best unit in our codex. But the question still remains of "How many Flesh Hounds is too many to have in a unit?"
The goals here are pretty simple.
1. Make it to the Assault phase with minimal losses
2. Successfully make the assault and destroy roughly over half of the unit you are assaulting.
3. Destroy the rest of the unit during your opponents assault phase, then consolidate towards their next target.
4. Rinse and repeat during your turn.
For the purposes of this math-hammer, we will be assuming that we will be facing a unit of 10 Space Marines, behind a defense line. (as the majority of things we will be assaulting will most likely be in cover of some sort)
Due to the lack of assault grenades, the flesh hounds will normally be at Initiative 1
(I'm going worst case scenario here, as attacking important units that are not in cover is of course a much better idea)
We will also be assuming that the Grimore on the Hounds was successful.
(Many People are still on the fence about whether the Grimore is needed or not, and with the number of Battle Reports I've read/watched, I would highly recommend one.)
On average, a unit of 10 Space Marines will kill between 2 and 5 hounds before they assault in, depending on rapid fire range.
20 Hounds vs 10 Space Marines
In close combat, 10 Space Marines will cause roughly .4 wounds to the hounds.
the Hounds will kill roughly 8.889. So almost the entire unit.
15 Hounds vs 10 Space Marines
In close combat, the Space Marines still only cause .4 wounds, so nothing significant.
The Hounds will kill around 6.667 marines on the charge, and then 3.334 in the next assault phase due to the loss of furious charge.
So as of right now, the unit of 20 looks to be the best option as 20 will start in the unit, between 18-15 will make the charge, and we're successful.
But here's where things get tricky because a lot of people also chose to run a Khorne Herald on a Juggernaut with the unit of hounds, to add in the AP2 weapon, myself included. Although I enjoy the Axe of Khorne and being able to Challenge an IC if needed and instant death him, but that's for a different article...
For arguments sake, lets stick with a base Herald on a Juggernaut with a Lesser Reward for the AP2 Weapon, and not worry about the locus or anything else yet.
His Hammer of Wrath hits are 50/50 against Space Marines (He's Cavalry, so don't forget he has these) wounding on a 3+, so lets leave that out for now as it's not reliable. After the first round of assault, he will be killing around 2.77 models.
Now if we add those two numbers together, a unit of 15 hounds and the herald, on the charge, will kill 9.445 models on the charge, which is extremely close to what we are trying to achieve, but one good round of dice rolling give or take and your left out in the open for your opponents, who have now just witnessed what your hounds are capable of, to unload everything they've got into them, which is what we don't want.
Now more math!
20 Hounds plus a Herald: We take roughly 4-10 wounds from shooting, putting us at around 17 hounds and a herald on the charge, which in my opinion is too many.
15 Hounds plus a Herald: We take the same 4-10 wounds from shooting, puts us at on average 12-13 hounds and a Herald on the charge, which is almost perfect, but I would like one more hound possibly.
10 Hounds plus a Herald: Now things are starting to get scary, as we could technically be at almost half the size of our initial size and we start to lose the cost benefits of the Grimore, and depending on what joins the assault we start to run further risks such as not putting out enough wounds to win combat, which would force Instability test, and being small enough to be wiped out completely by a vindicator or something similar.
I currently am running my units at either 15 or 16 hounds depending on points available, and it seems to giving me the results I am hoping for. At this point I think the locus could be over kill.
As always, more testing is always needed.