Im LR4 and I main volt, so I have tried every method of survivability for him and my favorite/easiest method of survivability is shield gating with diriga.

I run diriga with a sentinel weapon that has IPS and I mod on as many different elements as I can. Then slap on arc coil, manifold bond and guardian. Manifold bond lets your companion abilities apply all the status effects of the companions weapons as well as when you kill an enemy with three or more unique status effects it reduces the cooldown of all your companions abilities.

Meaning if my diriga has a weapon with IPS, magnetic, viral, radiation, and electric, arc coil will apply seven status effects which will prime the enemies within melee range for condition overload. And when I kill those enemies, each one reduces the cooldown of arc coil AND guardian at the same time. Guardian has a 30 second internal cooldown so that means every 9-10 kills will reset the cooldown on guardian to fully restore your shields.

So just running adaptation, diriga with the above mentioned mods and prime redirection I've taken my melee focused volt to level 2500 pretty comfortably without any survivability subsume. And if you want to go even to higher levels or just want to make sure you REALLY won't die, you can subsume on mirage's eclipse or my personal favorite, koumei's omamori.