I like the analysis on the seeker rush. I'll put down my opinion om it seeing as it's fairly new. While i'm at it, The Carbon Roller Deco and Rapid Blaster Deco too.
At long range, the enemy would of noticed a hoard of seekers coming towards them, Even if you aim the seekers while they're hiding, there would be enough room to maneuver, assuming if used defensively since in most situations you would be sending seekers into enemy territory. Its effectiveness tends to vary a lot, or you could be at the right place and at the right moment to get maximum effectiveness. Now putting into the context of the enemy team pushing, you'd need constant pressure to force the enemy to think twice about coming closer to a hoard of seekers. Though if the enemy is spread out, it might be tougher to accomplish since if one squid dodges a bunch and you're concentrating on another squid, you might find yourself in a bit of a pickle. So i think Active back was a good choice. Seeker rush is like Rapid Blasters at close range, if you can't aim it with its fire/deploy rate *Splat"... It's life or splat really.
Carbon Deco... Mmm, in my opinion. It still retains it's Assassin like qualities, but it has a less reliable escape with burst bombs and Inkzooka gone, so it can't be as effective on the killing front than the Normal Carbon Roller. Turfing front is viable, Seekers cover a decent amount of turf when used in the correct fashion, plus the main weapon itself is fast and can handle on it's on while spreading ink. It can be used on the back line defensively to ensure your side is always inked, plus seekers can put pressure on advancing opponents sorta like an active back. So combine what i thought, and you get mixed. That's how i see it anyway.
With the Rapid Blaster Deco, it was a good choice moving it from killing front to active back, there's hardly a chance for it if you're always trying to push, with an unreliable close quarters ability, it just can't last on the battlefield because it simply can't manage it. You could be surrounded, flanked, or generally aimed at by other killing front weapons. With two shots minimum i don't think it's possible to clear out the enemy team playing aggressively, i don't think you're always going to get two hits in, and Suction bombs can only do so much before you need to refill, which leaves you open if you can't manage your ink. So yeah Active back yay!