Ok I like to play Leblanc and I am considering two different finished builds rite now, I wanted to look at some numbers to help decide, playing against an imaginary enemy champion with 100 Mag Res when we are both level 18.
Calculations will be made assuming full stacks on stackable items.
Also, Abyssal Scepter will work because it's range of 1000 outranges all of LB's abilities, so the offensive Aura will apply.
Also, for simplicity I will ignore runes, assuming that in LoL utopia, runes of opposing champions will negate each other.
One of the builds is:
Will of the Ancients (spell vamp for survivability: imagine distort in a minion mob with 25% spell vamp, or >2k bursts with the same. Also for a decent amount of ap)
Sorcerer's Shoes (movement speed and MaP)
Rabadons (AP and amp up other AP)
Void Staff (Decent AP and MaP)
Rylais Crystal Scepter (Decent AP and CC)
One of my favorite combos with LB is to do q-r-w
So if I do this combo using this build,
I will do 245 + 0.6*(734.5), since I follow up with an r immediately, I get the bonus damge from sigil, doing 100 + 0.3*(734.5), then the r does (245 + 0.6*(734.5))*1.4, the q trigger's the repeat of sigil's bonus, dealing (100 + 0.3*(734.5))*1.4, using my w I do 245 + 0.6*(734.5).
This total sum is equal to 3064.22 damage.
This item set gives me a flat 20 MaP, and after the flat MaP kicks in, the void staff and my masteries will give me a 55% MaP, so instead of the original 100 Mag Res, my enemy champ will instead have (100 - 20)*.45, which is 36. This means the percent of damage they take is 100/(100 + 36), or 73.529
The damage the imaginary champion would take then is 3064.22*.73529, or 2253.103 damage.
My other build, which at the moment I prefer, is:
Will of the Ancients
Haunting Guise (MaP)
Abyssal Scepter (MaP & AP)
Redoing the previous combo, I will now do
245 + 0.6*(663) + 100 + 0.3*(663) + 1.4(245 + 0.6*(663) + 100 + 0.3*(663)) + 245 + 0.6*(663)
This pre-sum is equal to 2902.88 damage.
The imaginary champion will change from 100 magic resist to 40 first, and then with masteries it will change it to 34. Damage taken will change to 100/134*2902.88, and the enemy champion will take 2166.328 damage.
Notes of Deliberation:
Build 1's key advantages are this: MaP focus on percentage reduction means that it will be more useful against tank characters who have higher than average Magic Resist values. This lets her do high damage output against tank characters, and not just squishies.
In addition, the CC from Rylai's will help kill runners/survivors, especially when combined with Ethereal Chains. Using Distort with Rylai's to do true CROWD control can help in team fights, making LB who is notoriously useful for single target burst damage a bit more useful in team fights.
Build 2's key advantages are this: MaP focus on flat reduction means that most champions will have no effective MaP during engagements. This lets her do extreme damage output against squishies and anyone who's unfortunate enough to have less than 60 Mag Res. The above combo does over 2902.88 damage to such champions, considering champions like Ashe and Vayne have a base health of less than 2k at level 18, this is a kill burst, and if they escape because of health boost or Mag Res items, Ethereal chains should guarantee a kill. In short, Build 2 has almost a guaranteed kill burst on squishies. Using it to take out carries in a team fight can make a big difference, and using it to kill a squishy in like .2 seconds during a 1v1 engagement is entertaining.
During team fights, Abyssal Scepter's aura can be helpful if your team composition involves other AP damage.
So key points from these two long sections:
Build 1 is better for attacking tanks for high damage, but not necessarily a kill, and Build 2 is better for disabling squishies via close to guaranteed close to instant deaths. Build 1's team fighting focus is for multi target high damage hits that apply cc and getting tanks. Build 2's team fighting focus is for debuff from offensive aura and getting carries/mages.
Certainly they might fit different play styles better, but I would like to know which of these builds the community thinks is better. Also, if anyone has any other uncommon LB builds they recommend, please post it as a reply.
EDIT: Neither builds are listed in the actual order I buy the items in, and they represent final builds, i.e. near endgame. Sorry
**** banshee's veil