...But you do
not need that much Bomb Defence; I only run one sub to counter Inkjet and Missiles. Also I'm not sure if this is for the Hydra or the Custom Hydra, because there's honestly no reason for you to use the vanilla over the custom in my opinion - the Custom highlights its role as a backliner infinitely better.
Going back to the gear, however, I also don't think you need that many Ink Saver Mains; I would instead substitute one main for a main of Ink Recovery just to balance out perks and ensure that you are receiving the highest return for your abilities. The Run Speed main is fine by me, as every Splatling does benefit from some mobility. -The Ballpoint, Mini, and Heavy all warrant 2x mains of Run Speed, but you can get away with 1x or less on the Hydras because it's more perch-oriented, but it really depends on how you play the weapon. I also don't feel like QSJ is necessary at all, because most of the time it'll be your team dying and jumping back to you, and if you do manage to die, the worst thing a backliner can do, then you won't want to jump back to teammates as they'll typically be in the heat of battle anyway. Speaking of being the last one alive, Tenacity finds great use on backliners, so consider that as well.
Here's what I run for the Custom Hydra (With the Neo Octoling Boots). The Special Charge is a no-brainer with Ink Armour, but Tenacity gets an honourable mention. I should honestly run both and scrap the Swim Speed, but the extra repositioning mobility really does help this weapon, otherwise you move unnecessarily slow. I also like to run Object Shredder because the CHydra is my go-to Splat Zones weapon and people just love their Bubble Blower in that mode. It's also nice for getting rid of Ballers that try to push straight into you. On occasion, I also run Respawn Punisher if I feel like the map doesn't let people flank me very easily, such as in Ancho V Games; you should only run Respawn Punisher if you get a K/D over 3/2, which if you're using this weapon, I should certainly hope you're getting (honestly 3/1 because your "lives" are more valuable than your typical front-liner, but use your discretion). Lastly I have had some success with Thermal Ink, but given that the Hydra reliably kills at max range with a full charge and 3HKO, it's less necessary. On the Ballpoint, I'd insist on it.