Beastmasters are a great unit, and if the rumors are true, we will be seeing them here very soon in late march. I had been waiting on this one to do a review, hoping for an FAQ. However I will do a pre-faq review and later update it when GW comes along sometime in the new year with their updates.
The issue is on how Power from Pain deals with these units. As it stands and reads, the beastmaster unit cannot create their tokens, however if they somehow get one, they all are effected by the pain tokens. While this seems to be a general conscensous over the internet, I am of the beleif that they will allow beastmasters to create pain tokens, however only models with power from pain will be benefit from them.
The next issue with beastmasters are the beasts. We have no models. I have read (not yet seen) people taking advantage of this and creating huge flying models on flying bases that are large enough for flocks of razorwings to give cover to raiders. I find this a little rediculas, self centered, and a little ignorant (no the earth and heavens do not rotate around what you say and think). Lets wait on this one until we get a model before we can start claiming that flocks of razorwings are going to be on flying bases or are that big.
Issues aside, lets look at Beastmasters, they carry the same stat line as a hellion, which is decent. The have power from pain and night vision abilities. They come with a skyboard but count as beasts, not jump infantry. They do get the splinter pod beneath the skyboard however, which is nice. It gives the unit up to 10 poisoned shots at 18". However, you should probably be not be shooting, but instead fleeting your butt across the battlefield. They do not get a hellglaive. So no +1 attack or +1 strength. Your Beastmasters are in the unit simply to get more beasts, and to give them some leadership.
For each beastmaster in your unit, you can choose a group of beasts. All of which come with night vision and are beasts and as such fleet.
0-5 Khymerae
0-1 Clawed Fiend
0-2 Razorwing Flocks
Khymerae. WS4 BS0 S4 T3 W1 I6 A3 Ld5 Sv 6+ First off, the old warpbeasts models we have fit the Khymerae perfectly. So if you have those, here is probably where they go. Khymerae are half real beasts and come with a 4+ invulnerable save. This makes them invaluable in your beastmaster units. Any weapon able to double your razorwings flocks toughness, can be thrown on your khymerae. With 0-5 you really only need one of your beastmasters dedicated to the khymerae.
Clawed Fiends.WS4 BS0 S5 T5 W4 I5 A4 Ld5 Sv6+. Since you can only take one of these per beastmaster it makes the decision to take one a little harder. At 40pts, your not going to be able throw too many wounds on these guys. I like them if you take them in numbers, but then you are really limiting yourself to how many razorwing flocks you can take.
Razorwing Flocks. WS4 BS0 S3 T3 W5 I5 A5 Ld5 Sv6+. Whirlwind of blades means that those 5 attacks you get have the rending special rule. Since you can take razorwing flocks in pairs per beastmaster, you can quickly get 40 rending attacks on I5 with 8 flocks. With rending any to wound roll of a 6 counts as AP2 and always wounds regardless of toughness. It also adds d3 to the strength of your hit vs armor. This means that stranded transports can be overwhelmed by razorwings.
I prefer Beastmaster units in large numbers for an overwhelming force on the field. For approx 240pts, 5 beastmasters, 5 khymeraes, and 8 razorwing flocks is my so far favorite configuration. It is something like 78 attacks on the charge, 48 of which are rending. They also take wounds extremly well, as you really only need to one beastmaster alive to hold a decent leadership. From shooting and close combat, wound allocation is rough for your opponent and gives you the durablity that your units needs to get into combat. Other configurations are really fielding to taste, however razorwings with khymeraes are going to remain my favorite.
With multiple beasts, it is easy to frighten your opponents with units like this. People that are unsure about what units can do, tend to make mistakes. Beasts like these are great ways to overwhelm your opponent with units they are unsure of.
Overall I will be using beastmaster units once we get a little bit more clarity on the how they work and what the models really are. A little playtesting shows just how durable they are though. They can take a tremendous amount of fire, and cover a wide area with their large units. Multiple assaults are this units specialties, as entire platoons of guardsmen are overwhelmed and gone in a flash. Be careful when assaulting in cover as they do not come with grenades, however can assault 2x the distance when rolling for difficult terrain.