If I am all wrong my calculations provide evidence of it and I will edit this to say to disregard this.
EDIT: due to some confusion on why I say 62.5 armor this is what the 125 armor calculation is leaving out. If counting only crits it breaks even at 125 armor but if you included that a Zeal + IE will give 60% crit chance up from the current 50% it is 62.5 as the breaking point for when armor becomes less effective with the PBE version compared to the current live system. I am talking average damage output not limited to only crits.
New Recipe: [B.F. Sword + B.F. Sword + 1100 gold]
Total Cost: 3700g
Attack Damage increased from 70 to 80
[Removed] No longer increases critical strike damage.
[New Effect] UNIQUE Passive: Doubles your critical strike chance.
[New Effect] UNIQUE Passive: 20% of critical strike damage is converted to true damage.
Zeal items still have 30% crit chance.
So we have here effectively a change from
(.5A + .5x2.5A) x (100/(100+D)) To (.4xA(100/(100+D)))+ (.6x2Ax.2)+(.6x2Ax.8x(100/(100+D)))
A is attackers AD
D is the armor of the one being attacked.
I'll set A to 100 since 200 will come out to twice as much damage meaning only one set of data for A is needed. D will have sets of data for 0, 50, 100 and 200
0 armor has 175 for old and 160 for new
50 armor has 116.667 and new has 114.667
100 armor has 87.5 for old and 92 damage for new
200 armor has 58.33 damage for old and 69.333
I don't currently have time to calculate in LW as well but since the true damage on new infinity edge is calculated before armor or anythign else it just makes LW items a little less effective when combined with infinity edge. This is also soemthing that will be a case tby case situation due to live LW items beign bonus armor while PBE is total armor.
62.5 armor is the point at which new infinity edge starts becoming better than old infinity edge. This means that a level 12 jax with no bonus armor will be taking more damage.
My suggestion for actually achieving the so called stated goals of nerfing marksmen is nerfing the crit on zeal items to 25% from 30% in addition to all of the stated changes thus far.
If the crit chance on Zeal items were reduced to 25% meaning that with infinity edge it would be 50% crit chance down from 60% the breaking point of the new one would be 125 armor which is honestly the kind of change that would actually make a difference since basically any tank or fighter will have at least 60 armor by the time a marksmen would have 2 items completed.
I call bullshit on it being a nerf to the 2 item power spike. And you are making BotRK cheaper and LW items are total armor so health stacking is also less effective.
Damage creep is real. This might not seem like much but with how riot has done small damage increase like this in the past many times damage is substantially higher than it was in season 2.
I didn't make it pretty but here is the spread sheet with 1 Zeal + IE and 2 Zeal + IE.