Calculating the cost of Aura + Divine Blessing + Lifetap

Hello, I want to run Wrath + Divine Blessing + Lifetap + Increased Duration but am having trouble figuring out how the game decides the end life cost.

Things I've discovered:

The following modifiers change the end cost of the 4L wrath spell:

Flat changes to total mana
% changes to cost of skills
% changes to life cost of skills
% changes to mana reservation efficiency

The following modifiers do NOT change the end cost of the 4L wrath spell:

Flat changes to total life
% changes to mana cost of skills

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That all being said, I decided to come up with a working function that seems to break down however.

[Total Mana]*(reservation cost of aura)*(1.3)*3 + [flat divine blessing cost]*(total changes to cost of skills and/or life cost of skills)

Here the 1.3*3 multiplier comes from lifetap and increased duration (which will affect wrath due to lifetap gem)

So for my character, I have 1244 mana and wrath reserves 35% of my mana and 30% reduced cost of skills (15% reduced cost and 15% reduced life cost) and a lvl 7 divine blessing (135 flat cost added) So:

(1244)*0.35*1.3*3 + 135*0.7 = 1793 which is the correct value.

However.... when I unspec out of tireless (6% reduced cost) the new formula should be:

(1244)*0.35*1.3*3 + 135*0.76 = 1800. Yet my cost is 2177 in game.

When I unspec out of the life reduced cost of skills mastery (15%) as WELL as tireless (6%) my new cost should be:

(1244)*0.35*1.3*3 + 135*0.91 = 1820.

Yet my cost is 2331 in game!

It seems that the reduced cost of skills affects the cost more than I estimated. Let's say it affects both portions, the cost originating from the reservation and the cost originating from the flat mana cost from the divine blessing gem. Then:

((1244)*0.35*1.3*3 + 135)*0.7 = 1283.... This is wrong

Okay maybe the mana multipliers of increased duration and lifetap affect the flat cost portion as well and the % reduced cost affects everything too, so:

(1244*0.35 + 135)*1.3*3*0.7 = 1557. Wrong again.

Is there a bug or am I just missing something fundamentally important with the cost calculations?

Answer:

[[Total Mana]*(1.3)*3 + [flat divine blessing cost]]*(total changes to cost of skills and/or life cost of skills)

% reservation does not actually influence the end cost of the wrath spell.

I was wrong when I wrote that.