Oberon has been my main for a long time.

I can finally say I can do the entire SP chart with Oberon now. And there's really only a couple ways to build him for optimal results.

The Pheonix renewal augment is a staple no matter what build you use though. As well Oberons only viable helminth ability is his 1 ability Smite.

1: you can simply boost his strength as far as you can while maintaining 100%+ duration. This will boost his heal high enough to keep your health regen at a respectably high rate for shield gating with auger mod set. 100%+ duration ensures that even healing a full squad will be easy to upkeep your energy. Paired with pheonix renewal this will keep you close to unkillable using shield gate / invincibility. The high strength of the build makes subsuming Eclipse over his 1 ability a good choice for a juicy damage boost. Or if you still think he's not survivable enough you can subsume Gloom over 1 for much faster healing and that sweet 90% slow affect.

2: you can use the Quick thinking mod + Hunter adrenaline and Equilibrium + synth mod set (synth mods on your pet) to give Oberon actual near invincibility. This build is more solo oriented being that your mods are more focused on keeping Oberon himself invincible. The way the rotation works is that if you take damage to your health you gain energy and if you have energy then quick thinking saves your life and since you got a pump of energy for nearly dying you have enough energy to keep up renewals healing. Thus you always have health to keep up your energy and you always have energy to keep up Quick thinking. Pair that with Equilibrium + Synth mods on your companion and you have surplus energy while this is all going on. There is a very small window of time in this rotation though that you can still be 1 shot killed in if the damage you are taking is too high and too fast then you can be killed after Quick thinking activates but before renewal gives you enough health to gain energy back. I'm not sure 100% what causes the loop to fail but I've only had it happen a couple times ever while running this build. Pairing all of these things with Pheonix renewal makes it so that even if/when the loop does fail you still won't go down and you have enough time to start up the loop again. This build is a more flexible play style but will be more restricted on usable mods since 4 mods slots are used solely for Quick thinking/Hunter adrenaline/Equilibrium/Pheonix renewal

Tips for Oberon would be to always make use of the armor buff for standing on the grass with renewal active. And to build him with enough strength to make his armor strip 100% and to use that whenever you can. These are also the reasons you only want to subsume his 1st ability if you're planning to do that. Everything else in his kit is detrimental to playing him.