1Round 1
With the nerfs, Cosmic Coolant becomes even less of an option. i personally wasnt taking it before but now the path i was taking makes more sense with Stinger 3rd. You dont need a third wave of Torpedos to kill so we are not gonna stress it with Cosmic Coolant or Torpedo Glide. Instead we will focus on building full Ability Power and use Stinger in combination with 2 rounds of torpedos to kill people!
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2Round 2
Here on Round 2 we used to rush PulStar Destroyers with a Power Playbook, but now with the reduced 15% AP on Pulstar Destroyers that only nets us 115.5 damage on our torpedos against just building 40% AP that'll net us 119 damage on our torpedos, while also have extra cash to buy ability lifesteal and raw AP working towards our healing on torpedos as well (that the extra 20 on Pulstar doesnt provide).
So to make it short, we build full AP rare items before prioritizing PulStar Destroyers and it will still net us more damage! Its also good cause we can instead rush Lock-On Shield which gives us all the survivability we need for the next 4 rounds.
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3Round 3
On round 3 we take Stinger to synergize with all the raw AP we are building. Torpedos isnt the only thing you can do, and even before the nerfs Stinger was a better option for damage numbers.
We can get up to 60% AP rn meaning (85+85*0.6 = 136) or 40% AP + PulStar Destroyers meaning [(85+20)+(85+20)*0.4 = 147]
As you can see we can deal more damage with these set of items: Power Playbook + Nano Cola + Lock-On Shield + PulStar Destroyers. (147 dmg on torpedos)
IF you want to go full on torpedos thats a way of doing it. i however will recommend keeping it with full raw AP since it helps Stinger which is more consistent than the torpedos, and instead of going for that extra 10% ap to get to 60% we would take Vantage Shot which is INSANE stats for just 4000$. 20% worth of Weapon Power solves your lack of healing on primary fire, as well as synergizing with your now changed play pattern focusing on Stinger procs.
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4Round 4
Here the most AP we could buy would be 80% for 153 damage on torpedos but losing 5% Weapon Power (since youd' have to sell Custom Stock). VS Buying PulStar Destroyers and deal 157.5 on torpedos without losing that 5% Weapon Power. So we take PulStar Destroyers as its now the mathematically correct choice.
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5Round 5
Now, since we are using our currency to maximize our damage potential, and the basic foundations of our build are already, well, built. We'll start taking Powers that can help our survivability as well as giving us utility for our team. Thus we take Hyper Healer. This way we dont need to spend currency on Survival items and can focus straight up on getting more damage! This pairs especially great with our raw AP since Hyper Healer scales with AP! By now, instead of granting 50 Overhealth it should be giving us (and your team) 90 Overhealth!
For items, we want to buy Champion's Kit, you should have enough cash for it, but if for some reason you dont, you can buy Solar Shielding as a second option. It got nerfed but its still a pretty good option. Otherwise you can take Cybervenom as it will proc on your Stinger and Torpedos denying a TON of healing which by this point becomes a serious issue to deal with.
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6Round 6
Here's pretty easy, you want to sell your Custom Stock to get Cybervenom, it wont give you more AP but the healing reduction is a key factor at this point of the game. Think of it as like dealing 30% extra damage and you'll feel better buying it, which is only partially true anyways.
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7Round 7
If by this point you haven't won, something's going South. Maybe the enemy DPS are busting you down, maybe its the enemy tank. But for sure you are dying, so we'll fix that while keeping our AP scaling going with Lumerico Fusion Drive. Its an insanely good defensive item that still nets you 15% AP.
Then, you can take Blink Boosts to dodge Junker Queen/Dva/Genji/Reaper/Mei. or Rally Ring, to maximize your Hyper Healer value. i'd say you wanna choose this last power based on what's going on at your match, but as a good default Rally Ring is very good and doesnt suddenly change how you play the game like Blink Boosts does. So i personally take that one.
And thats the build! Juno actually got buffed in this last patch since she gets 33% more money from damage and healing, so with this build you should actually feel her to be stronger than before! You'll just wont be able to ONLY throw torpedos, now you'll have to shoot as well :)