Shaco's potential AP Burst at the time of the 3/24 PBE notes without runes/masteries
Alright folks, let's get into the nitty-gritty of ridiculousness that this will be.
#THIS ASSUMES RIOT GIVES SHACO BACK HIS AP RATIO ON Q
Pure AP Shaco
or 
460 AP + 35% from Rabadons = 460 + 161 = 621 AP plus 40 AD (Void Staff build)
480 AP + 35% from Rabadons = 480 + 168 = 648 AP plus 40 AD (Nomicon build)
With the Void Staff build, Shaco's burst rounds out to: 40% Backstab, 40% Deceive, 75% Shiv, for a total of 140% AP burst ratio.
140% of 621 is 869 damage plus 130% from backstab (117 base AD + 40 from Gunblade) leads to a total burst of: 584 magical (Shiv is magic damage, nothing else is and it has a 75% total AD ratio.) and 607 physical before Ludens, Gunblade proc, or Lich Bane for a total of 1191 mixed damage.
Including Gunblade, Ludens, and Lich Bane, we see that Shaco deals: Flat 250 + Flat 100 + flat 88 (75% of base AD on Lich Bane) 30% + 10% + 50% in ratios for another 438 + 90% AP ratio (559) Magical damage, leading to a total burst of: 1581 magic damage and 607 physical damage (2188 total mixed damage) with magic penetration added on.
AP Shaco with IE
380 AP + 35% from Rabadons = 380 + 133 = 513 AP plus 40 AD + 70 AD
With the Infinity Edge build, Shaco's burst rounds out to: 40% Backstab, 40% Deceive, 75% Shiv, for a total of 140% AP burst ratio.
140% of 513 is 718 damage plus 130% from backstab (117 base AD + 90 from IE and Gunblade) leads to a total burst of 540 magical and 602 physical before Ludens, Gunblade proc, or Lich Bane for a total of 1142 mixed damage However, we need to keep in mind that Infinity Edge increases Shaco's crit damage by 50%. Assuming that the bonus on Backstab is including AP, that would also go up by 50%.
So now we need to assume that bonus 50% to the original 269 gets bumped up by 134 to 403 and then add on an extra 102 for the 50% of that 40% AP (205) ratio for a true total of 540 magical damage and 838 physical damage. A total of 1378 mixed damage.
Including Gunblade, Ludens, and Lich Bane, we see that Shaco deals: Flat 250 + Flat 100 + flat 88 (75% of base AD on Lich Bane) 30% + 10% + 50% in ratios for another 438 + 90% AP ratio (462) Magical damage, leading to a total burst of: 1440 magic damage and 838 physical damage (2278 total mixed damage) of more damage that is harder to itemize against, but without the extra void staff penetration.
Look at how much of Shaco's burst damage is coming from purely items. Over 1000 points of damage. That is what made AP Shaco so ridiculous earlier. Not his current ratios, but the fact that he abuses three items that have AP ratios baked into their kit to make up for his lack of ratios.
Anyway, as you can see, the math pretty much checks out right there. AP Shaco with an IE will burst harder in mixed damage at the cost of not having extra penetration from Void Staff. Obviously it depends on how much MR your opponent is building, but if it's very little, IE is the way to go for burst damage. Also, take Lord Dominik's Regards in mind for groups building lots of armour against your AP Shaco.
2010 health level 18 Shaco vs a 3500 health tank? You're getting the full 15% bonus physical damage on your autos, which have the Backstab applied to them (I don't see why it wouldn't apply).
So at the risk of losing out on your crits, you're still doing a solid 269 + 205 = 473 backstab +15% bonus to 544 physical damage, and getting a lot more damage out of your AD build. While still not the 710 damage Deceive that it could be, it will do more damage to tanks that have a lot of armour for you to shred through (especially if you take that armour penetration addition into consideration.
But if there are no tanks amassing tons of one resistance, just stick with IE. It's your best build.
