Nashor's Tooth on Azir is a trap.
So recently I have been seeing more Azir play (probably because of the buff/him being played at IEM/what have you). There's something I had noticed and really thought about and then saw evidence of while watching Bjergsen play - he makes two Morellonomicons. Now, let's think about this, shall we? The de-facto item to go for has been Nashor's on Azir. Riot has said that even though he doesn't get the on-hit, the other stats are good for him. This may very well be true, but I am tired of seeing people rush this item and then be like "why do I DO NO DAMAGE?! I THOUGHT THIS CHAMP WAS GOOD WTH"
Well it's simple. Nashor's Tooth is a trap.
The item's cost, AP, and all other stats were created and balanced around the idea that you'd get additional mileage out of the magic damage on-hit. This makes it good for people like Teemo, Diana, etc who already have magic damage based passives attached to autoattacking.
Looking at Azir though, I think the build path is pretty clear. Morellonomicon into dcap/zhonya's/damage item. This is also supported by a couple of Azir's earlygame patterns. In the early game, you're not going to have as much time to have soldiers sit and AA, in general - you're going for a Q into one or two AAs for your poke pattern, and maybe soldier AA Q AA if they're closer to you. This means that building a needlessly large rod item (zhonya's or dcap, I wouldn't think DFG but it could be a good source of additional cdr/aspd and some burst potential) is going to net you more damage in general. And then what? Well, I still don't think Nashor's is a good choice.
So you made a dcap? Probably should make a Zhonya's for the escape. Made a Zhonya's? Probably should make a dcap or void staff to scale your damage into mid/late. I personally make Athene's because I feel the stats are more beneficial to Azir than Nashor's - but my understanding is that Athene's isn't generally what people build midlane anymore.
My point is mostly that you definitely shouldn't rush Nashor's. It probably shouldn't be your second item. I see this item as a lategame powerspike for Azir, if purchased on him at all - "my soldiers are getting a lot of opportunities to AA so I need the additional aspd and CDR to get as many hits in as possible". But please, please, stop rushing Nashor's Tooth in games. Stop rushing RoA. Morellonomicon is the way. (or Athene's if you're oldschool). And then DAMAGE. Take advantage of the Q and ultimate AP ratio's rather than trying to force yourself to gamble for additional soldier hits.
it's cheap, but already has most of the AS and the CDR.
, it's way more efficient on Azir than 




any of these last three can switch order, since you may sit on t1 boots for whole game and build ga earlier b/c you need survivability).
