HJK is nearly double the base power of Drain Punch. Honestly speaking, Zuruzukin doesn't have remotely near as much aptitude for DD sweeping without it. It really is a tough situation, because with it he has the attack power he needs, but he's also vulnerable to residual damage, Ghosts, and the ever-present chance of LOL THE ATTACK MISSED.
Also, it is still a matter of hope. With Team Preview, you see that your opponent might have X pokemon, but it still comes down to a game of rock paper scissors. For example, you see that your opponent's team includes a Roopushin and Burungeru, Roopushin switches in on the turn you DD, SS and SR are in play on both sides of the field. Do you go for the kill with HJK? If you do he might switch to Burun and you'll lose half your health, if you predict switch and crunch/icepunch he can just Drain Punch you dead. 'Predictions' imply a lack of failure, but in reality it's just a fancy word for 'guess'. Also, what kind of Roopushin are we talking about here? Guts Orb, I assume? Forgive my being skeptical, but I just find the idea that base Zuruzukin survives a SE 90 power physical attack coming from Roopushin far-fetched, especially if you factor in at least 2 turns of SS damage (switch in and set-up) and SR damage beforehand, and another turn of SS along with LO recoil afterward.
Furthermore, if Politoed is one of the most used pokemon, why is he the one to be calced? Politoed is the backbone for Rain teams, there is no feasible reason why he'd be sent in on a setting-up Zuru over something like Kingdra or Skarm. Politoed vs Zuru implies that Zuru is the one who was sent in, meaning he could have taken an attack on switch, (or not if Politoed and Zuru switch in together, or Politoed KO'd something.) taken an attack on setup, and taken an attack in response to the HJK/Drain Punch. You said it takes Politoed 2 hits right?
There is a lot more context to pokemon teams than "Here's the most used OU Pokemon. Every team consists of these pokemon slapped together in different orders."