I'd like to add my thoughts on how to improve the existing mages.

1.  If there is going to be any hope of getting a small swarm from the warlord going, there needs to be more in-school level 2 soldiers.  He just doesn't have the mana supply (even with meditation amulet) to hope to get a barracks build working right in a short enough time with level 3 creatures and the level 1 creatures at his disposal just aren't up to the job without help.  Butcher is nice, but he needs more for the strategy to see merit.

2.  There needs to be a nature school 'attack spell' for the johktari beastmaster to become truly competitive and play to her strengths.  It wouldn't have to be anything ridiculous like hurl rock, just something that doesn't require her to spend 30+ points in the book on attack spells.  Even with only one spell, it would likely cut her attack spell points used down to below 20.  I almost cried when I saw that she couldn't use burst of thorns because it was so perfect for her (minus the vine token part).

3.  Resilient is just plain too beefy.  I get that resilient creatures are supposed to be tough to kill, but it is too much right now.  Even the old Iron Golem(which, I believe nobody will dispute, is already a top tier card) pales in comparison to a zombie brute, and the brute can move and attack on his own!  There needs to be some kind of counter, other than the usual 'Don't be there', or 'Rush the mage' arguments.  +X vs nonliving is not enough either as the bonus dice are too unpredictable.  There needs to be some kind of direct counter like there is for incorporeal.  A 'critical damage vs. nonliving creatures' attack trait would not be out of line if used sparingly and tastefully.

I have been inspired by the analysis done by fas723 and lettucemode to create my own analysis.  With the rise of spawnpoints lately, this analysis focuses entirely on the mana efficiency of attacking creatures and conjurations.  Please read the Limitations section before attempting to make any sense of the results.

Methods:
I first started by separating each relevant attack from the creature or conjuration and perform simplistic statistically averaged attack against a set of hypothetical defenders to calculate the expected damage.  There were 8 defender configurations that were chosen... 0 Armor, 2 Armor, 4 Armor, and Resilient, 0 Armor Aegis 1, 2 Armor Aegis 1, 4 Armor Aegis 1, Resilient Aegis 1.  In this calculation, resilient means the same thing as arbitrarily large armor.  Once the attacks were computed, the average of the attacks were calculated and stored for the rest of the calculations.  The efficiency score of the is then computed by dividing the average projected damage by the mana cost of the creature or conjuration.

To calculate best general attack efficiency, the highest scoring attack for each creature or conjuration is selected and ranked according to it's score.  Similarly, the best general weakest attack efficiency is the lowest scoring attack for each creature or conjuration ranked according to it's score.  These two scores should provide upper and lower bounds to the true score of a creature.

Equations Used:
1:  Dice Rolled = Attack Dice - Aegis Value
2:  Expected Crit Damage = 1/2 Dice rolled
3:  Expected Damage = Number of Strikes * MAX( Dice Rolled - MAX( Armor - Piercing : 0 ) : Average Crit )
4:  Average Damage = ( Expected Damage for 0 Armor + Expected Damage for 2 Armor ... ) / Sample Count
5:  Cost Efficiency = Mana Cost / Average Damage

Limitations:
Attacks that have a trait that directly affects the number of dice rolled or damage dealt vs armor were applied where applicable.  The traits included in the calculation include charge +X, piercing +X, +X vs Type(+2 vs flying), critical damage, bloodthirsty +X, doublestrike, triplestrike, sweeping, and zone attacks(calculated vs at most 3 defenders).  Many other traits are left out of the calculation such as burn, corrode, unavoidable, ethereal, and so on because they represent more tactical lines of play, which is outside the scope of this analysis.

There is no way to know how likely a given attack is usable in the general case (if even at all).  As such, the best I can do is provide a maximum and minimum score from the best attack and the worst attack and let you guys figure out for yourselves where the true value actually lies.

Finally, before taking note about about the efficiency of Ballista, remember that this calculation does not factor in tactical play, and that includes the fact that it can only attack every other turn at most.  It was calculated the same way that other creatures were.  That said, an argument could be made that no creature is guaranteed to attack every turn in all cases(except possibly Grimson).

Top 50 Results:

Best General Attack Efficiency			Best General “Weakest” Attack Efficiency
Rank	Name	Score	Rank	Name	Score
1	Ballista	0.461	1	Ballista	0.461
2	Vine Snapper	0.446	2	Goblin Grunt	0.391
3	Feral Bobcat	0.438	3	Akiro's Hammer	0.391
4	Akiro's Hammer	0.427	4	Raptor Vine	0.319
5	Dwarf Kriegsbiel	0.398	5	Bitterwood Fox	0.313
6	Goblin Grunt	0.391	6	Skeletal Minion	0.313
7	Zombie Crawler	0.391	7	Vine Snapper	0.313
8	Ludwig Boltstorm	0.361	8	Iron Golem	0.279
9	Shaggoth-Zora	0.359	9	Orc Butcher	0.273
10	Oscuda	0.346	10	Shaggoth-Zora	0.273
11	Zombie Brute	0.330	11	Skeletal Sentry	0.273
12	Temple High Guard	0.323	12	Thunderift Falcon	0.260
13	Raptor Vine	0.319	13	Timber Wolf	0.243
14	Bitterwood Fox	0.313	14	Zombie Crawler	0.234
15	Skeletal Minion	0.313	15	Blue Gremlin	0.232
16	Zombie Minion	0.313	16	Thornlasher	0.223
17	Darkfenne Hydra	0.293	17	Zombie Minion	0.223
18	Unstable Zombie	0.292	18	Nightshade Lotus	0.223
19	Iron Golem	0.279	19	Bridge Troll	0.221
20	Steelclaw Grizzly	0.276	20	Devouring Jelly	0.221
21	Mountain Gorilla	0.273	21	Knight of Westlock	0.221
22	Orc Butcher	0.273	22	Skeletal Knight	0.221
23	Sir Corazin	0.273	23	Earth Elemental	0.219
24	Skeletal Sentry	0.273	24	Deathfang	0.203
25	Thunderift Falcon	0.260	25	Darkpackt Slayer	0.202
26	Goran, Werewolf Pet	0.250	26	Dwarf Kriegsbiel	0.199
27	Timber Wolf	0.243	27	Zombie Brute	0.199
28	Bloodcrag Minotaur	0.242	28	Temple High Guard	0.198
29	Grimson, Deadeye Sniper	0.242	29	Asyran Defender	0.195
30	Dire Wolf	0.240	30	Invisible Stalker	0.192
31	Tarrok, The Skyhunter	0.240	31	Accolyte of the Bog Queen	0.188
32	Earth Elemental	0.234	32	Asyran Cleric	0.188
33	Blue Gremlin	0.232	33	Brogan Bloodstone	0.188
34	Kralathor, the Devourer	0.227	34	Darkfenne Bat	0.188
35	Goblin Slinger	0.223	35	Feral Bobcat	0.188
36	Thornlasher	0.223	36	Firebrand Imp	0.188
37	Venomous Zombie	0.223	37	Goblin Builder	0.188
38	Nightshade Lotus	0.223	38	Psylok	0.188
39	Bridge Troll	0.221	39	Steelclaw Grizzly	0.184
40	Devouring Jelly	0.221	40	Oscuda	0.183
41	Highland Unicorn	0.221	41	Ravenous Ghoul	0.183
42	Knight of Westlock	0.221	42	Grey Angel	0.182
43	Skeletal Knight	0.221	43	Whirling Spirit	0.182
44	Spitting Raptor	0.216	44	Ichthellid	0.181
45	Selesius, The East Wind	0.208	45	Necropian Vampiress	0.180
46	Deathfang	0.203	46	Redclaw, Alpha Male	0.180
47	Darkpackt Slayer	0.202	47	Emerald Tegu	0.174
48	Skeletal Archer	0.199	48	Unstable Zombie	0.174
49	Royal Archer	0.198	49	Togoroh, Forest Sentinel	0.173
50	Asyran Defender	0.195	50	Thorg, Chief Bodyguard	0.169

I have probably forgotten to include important information on my methods.  Please ask you you have any questions or feedback, enjoy the data, and remember that it is only a guide.