Why exactly do ppl build Morello on Azir?

[According to OP.GG everyone builds Morello on Azir.](http://eune.op.gg/champion/azir/statistics/mid) [Lolking guide author who is in Master says: "You always want to build Nashors > Sorc Pen Boots > Morello's"](http://www.lolking.net/builds/azir-build/428179/8.8-Mid-Lane-Kingdom---Azir-Mid-Guid) Apparently, many ppl think that {{item:3165}} on {{champion:268}} is a must. Why exactly? I fail to understand it... My thinking is, Morello is only really good against sustain champs bc of its grevious wounds. But if you're not against any sort of Vladimir, then why? How is Morello better than any other option? {{item:3027}} gives more AP, more HP, and a nice passive. Even {{item:3151}} would seem to me to be better since it gives same HP, same AP oh and burns the enemy. Yes - Morello has flat MR penetration. But this is how I get it: MR is a flat magic damage reduction. Flat MR penetration removes a flat portion of MR, so... +15 flat MRPen effectively means +15 magic damage. But only 15 damage is few, hardly appropriate to justify an item choice on its own. Azir's Soldier deals 60% AP per attack. Fully stacked RoA is 100 AP; Morello only gives 80 AP. Thus MOrello's contribution to Azir's damage is 60%*80 + 15 = 63. RoA's contribution is 60% * 100 = 60. This is only 3 damage less in return for many RoA's benefits Morello doesn't give! Liandry gives 60%*80 = 48 damage from AP and burn... 3 ticks of 1% of enemy's max HP. Assume the enemy has just 1000 HP... then we have 3 ticks of 10 HP... which is 48+30 = 78 damage total. Now we have overwhelmed Morello's flat magic pen pretty badly. Spellbinder even! It gives 120 flat AP. This means its contribution to Azir's damage is 60% * 120 = 72. Again, Spellbinder's flat AP overwhelmes Morello's MR pen badly. So as I said, on paper I fail to see any other use of Morello than to counter sustain champs. Yet that I don't see such a use doesn't mean there is none. So, might I ask, why is it recommended to almost always build Morello on Azir?
Report as:
Offensive Spam Harassment Incorrect Board