That's the thing, though, going for a strong AP build is even more important in something like Nemesis, where anyone with a champion that can hard carry
needs to. Once again, RoA isn't bad, but it's also nowhere near the best for an APC.
If you get RoA, that leaves you with two options:
1. Don't get a MP regen item. Congrats, you just stopped yourself from hitting the CDR cap on a champion that has CDR as a core stat.
2. Get a MP regen item. Congrats, you just made your build needlessly redundant.
As well as:
1a: Don't pick up Rylai's. Congrats, you just stopped yourself from getting an item with excellent synergy with your soldiers and a big chunk of AP in exchange for a mediocre chunk of AP and non-combat stats.
2a: Pick up Rylai's. Congrats, you're now spending a substantial portion of your gold stacking HP on an APC.
Do you understand the concept of opportunity cost? I'm normally one for looking into alternate builds, but between Azir being so absurdly strong with a good build and Nemesis mode ensuring that you've got a dearth of carries, I'd almost be tempted to call turning a carry into a knockoff Maokai in that context trolling. When they give you Karma or Morgana do you pick up a support item and go for Sightstone second item?
I mean, I get that it's sort of meant for fucking around, but when you're even getting to the point of talking about stacking mana on Azir and NOT picking up an Archangel's to at least make that mana worth something... if you're going to build random shit, at least try to synergize it. I mean, hell, I've built tank support Sona in Ranked and made it work, but this is still sort of WTF-worthy for me. o.0
Tank Azir doesn't work terribly well because of his lack of effective CC and base damage. He's got his knockup on the dash, and he's got his ult. The former requires him to already have soldiers out behind the enemy, or else to be almost in melee range, and the latter requires him to dash or burn flash for an Insec which is a really bad idea, since it has a shorter range and isn't single-target, meaning you've likely just dumped the enemy frontline into your team. The peel he can perform can be done just as well by an AP Azir.
Likewise, he's got nothing to really make people care about him. Bruisers and tanks tend to be what they are because once they're in the enemy team, they can do enough damage that they can't be ignored; some are like Jax and Irelia and are pretty much carries as well, others are like Renekton, Mundo, or Nasus and have good damage and AoE even when building full tank, &c. &c., and what all of those have in common is that they have at least two of a) reliable damage in their kit (rather than from items), b) reliable CC, c) gapclosers or inbuilt tenacity or both.
What does tank Azir offer that makes him a better choice than the normal hypercarry Azir, or than the other champions your team is likely to get who can build tanky? A Braum or Thresh is already kitted out to tank, and (with the exception of a handful of good players)
cannot be built to hypercarry in the same way that Azir can. Take that match you linked specifically: Your team already had a good AP Tank (Maokai), as well as Urgot (who is naturally a sort of off-tank anti-carry, though he probably didn't know what he was doing, given that he build Tabi against an AP team) and two weaker mid-range mages with heals. Your team had nobody except him (and Urgot if he landed Es) for long-ranged harass and poke. Instead of that random shit he build, he could have had Morello and a good chunk of Deathcap. Though perhaps I'm expecting too much, given that he only had 33 CS at 21 minutes.
Though in the end it didn't really matter, given that you had superior poke anyways (and judging by the tracker, were shoving every lane hard for the first half of the game). Meh. To each their own, I suppose. I'll agree to disagree.