You can swap the umbra polarity for a D polarity at no penalty.

Keep up your 2 and 3, and use Pillage to strip armor/shields and build overshields for defense. This build's main defense is just killing every enemy before they can hurt you, but if your shields do get popped (or if you get a nasty debuff like toxin or magnetic), immediately use [Rolling Guard].

Although this build isn't really using shield gating like [Brief Respite] builds do, I would still recommend equipping a decaying dragon key.

Some alternative Helminth options:
Xata's Whisper — Good for sentients.
Dispensary — Nice for bounties and other low-level content where you'll be staying in one area for a long time, but do NOT use this in Index or health and energy orbs will stop spawning.
Eclipse — This isn't always reliable, but both buffs are good. I would generally stick to Pillage, though, if only because it is more reliable.

Regulars Build

[Regulators] is currently set to radiation, but I recommend swapping elements depending on who you're fighting.