A lot of my games are played with Beastmaster, and I could give you the run-down on each card, but I don't know if that's really the most helpful thing to do. I'd be more interested in hearing about why you were losing to the Priestess, and what you think you can do to fix that.
In my experience, flexibility and power are somewhat at odds in this game. We all want to be able to make dazzling plays of mental acrobatics, but sometimes the path to victory is summoning a pet falcon and two Steelclaw Grizzles and just tearing the other guy to pieces.
That's not to say there's no room for cleverness or strategy, just that when I play Beastmaster, I play it as an agro deck, and if my opponent is defending well, only then do I get subtle.
---
One way I categorize Beastmaster books is by their conjurations. The one I play has none. This isn't because I think that's obviously better, it's just the way the book evolved. But I really like the idea of a Battle Forge in Beastmaster, and I think you should run with it. Forge has the smallest mana cost of any of the extra action conjurations, and is ready to go every turn.
I do sort of wonder if there isn't more equipment you could add to better take advantage of the forge. Dancing Scimitar? More armor? Elemental Cloak? Any of the equipment from the new expansion (I don't own it yet either)?
---
The Beastmaster book I play is a bit non-standard, but I'm pretty happy with it. I'll paste it here
not to say that it is what you should play, but to give you an example of what I mean about trading in versatility for power. For example, I don't have Cobra Reflexes, or Bull Endurance, or Regrowth, or Retaliate, or Call of the Wild, or Charge, or Group heal. I've got 2 Bear Strength, 2 Vampirism, and 2 Rhino Hide.
You'll see that my action advantage generator of choice is Fellella, though to be honest I only get to cast her when I'm already winning. I think Battle Forge may be a stronger initial play, but I'm playing so many enchantments that I cant quit her.
Things I wish were in here but aren't:
2 more Teleports (So spellbook-expensive, but soooo good. My candidate for best card in the game.)
2 Dire Wolf (don't own expansion yet, probably will replace a Bear and the Timber Wolf)
1 more Reverse Attack
1 Geyser (for Warlock and Priest, and just finishing off injured critters, or dazing unsolvable problems)
1 Chain Lightning (for Iron Golem)
1 Sniper Shot (For my Gorgon against Forcemaster or Priestess)
1 more Falcon
I could add most of the wishlist by cutting 1 Gorgon, and get nearly all of it by dropping Gorgon entirely, but Gorgon solves so many problems for me: range, flyers, big creatures, small creatures, soloing opponents, scaring turtling opponents into attacking, scaring midrange decks into attacking too soon, etc, etc.
Total Cards: (52)
Total Spellbook Cost: (120)
Mage:Beastmaster (Core) Attack: (2)Force Hammer x2
Conjuration: (0)
Creature: (10)
Bitterwood Fox (Core) x1
Fellella, Pixie Familiar (Core) x1
Gorgon Archer (Core) x2
Steelclaw Grizzly (Core) x3
Thunderift Falcon (Core) x2
Timber Wolf (Core) x1
Enchantment: (20)Agony (Core) x2
Bear Strength (Core) x2
Cheetah Speed (Core) x2
Eagle Wings (Core) x1
Jinx (Core) x2
Maim Wings (Core) x1
Marked for Death (Core) x1
Mongoose Agility (Core) x2
Nullify (Core) x2
Reverse Attack (Core) x1
Rhino Hide (Core) x2
Vampirism (Core) x2
Equipment: (8.)Bearskin (Core) x1
Enchanter's Ring (Core) x1
Gauntlets of Strength (Core) x1
Leather Boots (Core) x1
Mage Staff (Core) x2
Regrowth Belt (Core) x1
Ring of Beasts (Core) x1
Incantation: (12)Battle Fury (Core) x2
Dispel (Core) x3
Dissolve (Core) x3
Seeking Dispel (Core) x1
Shift Enchantment (Core) x1
Teleport (Core) x2