War Mechanics and the Runepriest

 I struggled to find a good breakdown of the mechanics in Warhammer here is what I have found so far relating to the Runepriest.

Action Points:
Characters regenerate 25 AP per second in game when not in global cooldown from using an ability.  Items that give +AP regeneration increase this value. So +5 AP regen is a 20% boost to action point regeneration.

You do not regenerate AP when casting a spell even if you are outside of your GCD. The GCD as far as I can tell is 1.5s, possibly a little less.

To make the most of AP regen you have to pause casting, or instead of spam casting, wait a second between casts to allow for an AP tick.

Morale:
Builds in combat.
Lowers outside of combat.
Using any morale ability will eat your whole morale bar even if it is just the first tier morale ability and you have all abilities available.

Player Attributes:
The cap for players at level 40 is currently 1,050. Source.
After this it takes 2 points to effectively increase that stat by 1 point.

Willpower
Willpower / 5 = Increases Healing Per Second.
Willpower / [(Level * 7.5 + 50) * 13.5] = +% Disrupt spells

Healpower
Healpower / 5 = Increases Healing Per Second
This stacks over the soft willpower cap at 1050 for no penalty. You are also likely to get more healpower than willpower because it is a cheaper stat due to not contributing to +%Disrupt. 

Intelligence
Intelligence / 5 = Increases ability damage DPS
Reduces chance for spells to be disrupted. Unable to find a formula.
*Doesn't seem to increase chance to crit as described.*

Toughness
Toughness / 5 = Reduces damage by X DPS

Wounds
 Wounds * 10 = Extra Health over default increase per level.
Wounds renown talents cost twice as much as other points so avoid buying those. However wounds is one of the strongest survivability attributes for RvR and you may wish to stack lots of it, including talismans.

Initiative
[(Level * 7.5 + 50) / 10] / Initiative = base % to be critically hit.
Initiative / [(Level * 7.5 + 50) * 13.5] = +% to evade.

Weapon Skill
Weapon skill / [(Level * 7.5 + 50) * 13.5] = +% to parry.

Armor
75% * (Armor / (Level * 110))

The cap at Rank 40 is 4400 - the character sheet tooltip shows 100% physical damage reduced, meaning the maximum 75% physical damage mitigation from armor. Armor works after Toughness mitigation.

Magical Resistances
Resistance Value / (level * 42) = % Resistance
Soft cap at 40% or 672 (Lvl40). After this it looks like it drops in effectiveness by a third. Source.
Hard cap at 75% but if you go over this value resistance debuffs will affect you less or not at all. Not confirmed.

Parry
Chance to parry melee attacks

Dodge
 Chance to dodge ranged attacks

Disrupt
Chance to disrupt magical attacks

Crit
Healing Crits - Base healing crit is thought to be 10%. Crit heals land for 150% of the base.

Damage Crits
There is no base chance to crit, but there is a base chance to be crit. This is determined by your initiative (see above). Your +crit% items are then added to that players chance to be crit to work out the final value.

See this thread on WarhammerAlliance.com for details.

Absorb Shields
Shields like Rune of Shielding and Ancestor's Echo absorb their stated amount of damage. They work after toughness is deducted from the damage but before armour/resists are calculated.