Here is Leviathan [Hydroid]!
I'm just trying to make Hydroid not completely worthless in endurance missions.
Primary weapon: https://overframe.gg/build/108819/
Secondary weapon: https://overframe.gg/build/108824/
Melee weapon: https://overframe.gg/build/108826/
Companion: https://overframe.gg/build/108830/
While it might be more expensive than it's worth for [Hydroid], you might find that this build is actually a lot of fun.
Use tentacle swarm to crowd control enemies, tempest barrage and [Kuva Brakk] to strip armor, breach surge enemies for extra crowd control and damage (use [Vitrica] on these enemies to amplify the sparks). Tidal surge isn't that useful in this playstyle, however you can still use it to throw enemies back from if absolutely necessary. Use [Kuva Kohm] on enemies once their armor has been stripped. You can use [Rolling Guard] to try and get yourself out of a sticky situation, but if that fails the [Djinn] sentinel can probably revive you.
I suggest running either zenurik or naramon. Zenurik for energy, Naramon for melee combo.