(Pulls out "target dummy DPS" spreadsheet)
The Wolf's 2 armor gives it an amazing advantage in any 1v1 combat. Let's look at the numbers:
Wolf (4 dice, 0 piercing) vs Skeleton (11 HP, 0 Armor):
[ul]
[li]Average 4.00 damage/round[/li]
[li]Average 2.75 rounds to kill[/li]
[li]14.1% chance to kill within 2 rounds[/li]
[li]70.0% chance to kill within 3 rounds[/li]
[li]95.4% chance to kill within 4 rounds[/li]
[li]99.6% chance to kill within 5 rounds[/li]
[/ul]
Skeleton (4 dice, 0 piercing) vs Wolf (10 HP, 2 Armor):
[ul]
[li]Average 2.59 damage/round[/li]
[li]Average 3.86 rounds to kill[/li]
[li]2.3% chance to kill within 2 rounds[/li]
[li]25.0% chance to kill within 3 rounds[/li]
[li]60.7% chance to kill within 4 rounds[/li]
[li]85.0% chance to kill within 5 rounds[/li]
[/ul]
For obvious reasons, 2 armor is really good against a non-piercing attack. However, it is really bad against a Piercing +2 attack (ie Dark Pact Slayer). There are also plenty of curses, poison, Burn damage, and other things that don't respect Armor. Against those attacks, the Wolf has 1 less health and costs 1 more mana than a Skeleton. The Skeleton is also Nonliving and Psychic Immune which protects it from various bad effects and spells.
Basically, the skeleton is an inferior toe-to-toe combatant but has various immunities. It's what you'd generally expect from a Skeleton.
On another spreadsheet-related note:
A Hydra's triplestrike (3 dice x 3) is equivalent to:
9 dice (9 avg damage) vs. 0 Armor
7.85 dice (6.89 damage) vs. 1 Armor
7.24 dice (5.44 damage) vs. 2 Armor
7.32 dice (4.83 damage) vs. 3 Armor
7.63 dice (4.57 damage) vs. 4 Armor
Oddly enough, only the first Armor point really has a strong disproportionate effect on soaking Triplestrike. Adding more than 1 Armor decreases damage taken by a far more modest amount.