Standard Hariyama is 80 HP / 176 Atk / 252 (insert defensive stat here), I don't know where you got "Hariyama shouldn't run attack EVs" from because it's simply not true. When you have base 144 HP, you really don't need all that much HP.
vs. 0/252 Calm
320 Atk vs 109 Def & 641 HP (60 Base Power): 378 - 446 (58.97% - 69.58%)
vs. 0/252 Bold
320 Atk vs 119 Def & 641 HP (60 Base Power): 348 - 410 (54.29% - 63.96%)
Anyway, this is kinda irrelevant for the most part, as Chansey's never going to stay in on Hariyama anyway.
Thats the OU standard. The most common UU "wall" spread is Purely defensive, unless its some Gimmicky Guts CB set of some sort (which are just not good/outclassed by everything).
The reason for this, is that it
NEEDS those EVs to counter Blaziken (All, minus Swords Dance, Brave Bird, and Specs Variants). Most people (EUM for example) have confirmed that they use that (max/max) Hariyama on their Stall teams to counter Blaziken, who runs rampant through most stall teams. Hariyama is still a decent tank, however it is just has terrible defensive typing compared to Registeel, Chansey, Steelix etc.
Its only/main selling point is its ability to counter Blaziken.
My point with Hariyama, is that its not the "best" way to take out a Chansey Quickly, as it can still outstall with wish, or Pass wish through a Bulky Hariyamas attack.
Guts Hariyama is the best exploiter of Chansey I have ever used in UU, hands down. Toxic / T-Wave boosts its attack to sky-high levels whilst Seismic Toss does very little against its humongous HP stat. Even with Adamant and lots of Attack EVs, there are still enough EVs left to make it reasonably bulky on both sides, even able to take two STAB Psychics from most Uxie. I've actually been using it as a lead, with great success. Froslass will only ever get up one layer of Spikes against it, before dying to Payback + Bullet Punch, leaving Hariyama at full health. As for Crobat, I simply pair it up with Ampharos (seriously, that shit really works!).
I don't understand the appeal of it as a Blaziken counter though. Without the Fighting resistance you die to Choice Band and Swords Dance variants with Superpower. Sure you take Fire attacks well with Thick Fat, but that doesn't make it a good counter by any means.
The CB variant is hesitant to Spam Superpower, because that leaves it vulnerable to many free Ghost Switch ins. If the user happens to take a Superpower, it can easily switch out to a fighting Immune.
I do agree, its not a good "counter" for the CB variant, or the Specs. But it does counter the more popular growing set, Mix LO, which is the only set that really tears apart Stall teams (well easier anyway).
Honestly, Hariyama offensive potential is so underrated/overlooked it's not even funny.
Thats because its offensively outclassed by Hitmonlee/Gallade/Medicham/Anything, Due to its Poor speed.
Its Bulk is the main aspect, so Bulky Offensive sets arent uncommon. The issue is, that Hariyama has to take a Sweepers Slot, because it isnt Bulky enough to be a "Wall" while having offensive EVs.
Edit: This is not to say, CB/Offensive Hariyamas are bad, its just they need to take advantage of the Bulk. Attack EVs make it lose its versatility.
Azumaril is a bad Comparison for many reasons. Firstly, Azumaril has a STAB priority attack, to make up for the speed. Secondly, Azumarill has MUCH better defensive typing. As well, Azumaril has a quite a bit higher attack stat.