Equinox fullfills her role as a DPS nuker with an armor strip subsumed, but I think Night form is still lacking. I also feel that she is split in a way that doesn't exactly fit with the current designs of warframes. It feels like you're often punished for swapping forms unless you have Energy Transfer, and even that doesn't carry over her augment for Pacify and Provoke.
With my following suggestions, I've taken careful consideration and tried to understand how Pablo designs his warframes as seen in Brozime's interview with him a year ago.
For her 1, make the buff she receives an aura that applies to allies (the speed/shield buff) and remove the diminishing strength of the buff with time aspect. Personally, I'd probably replace the shield buff with an increase to shield recharge/decrease to delay. Reduce the buff's duration to 10-15 seconds to encourage swapping constantly. With her Duality Augment, remove the 300% damage and give the Specter all your current active abilities of the opposite form and give them 4 seconds of invulnerability affected by duration. Also have the Duality Specter mimic Equinox whenever she casts her 4th ability.
I believe her 2 should be a tap and/or hold. Tapping will be the same as now, but holding the ability will make an aura that applies the effects of Rest and Rage to all enemies in an AoE Aura around the player when Equinox kills an enemy. So for example, if you shoot a guy while in Night form, it'll proc Rest on every enemy in the aura's AoE. Same for Rage. The Augment would function the same. This could make Equinox feel very AFK incentivized, so I think it should drain energy once per enemy for Rest and drain per enemy during Rage capped at 3 enemies (for the drain, not enemies affected). I also feel that the debuffs from the aura proc should be half of the duration of the tap cast. This means that Equinox will have to kill Enemies actively if she uses her Rage debuff on too big of a crowd to maintain her energy economy.
For her 4th ability, I think it should make all of her auras carry over to her other form (activating her 1) as a brand new synergy to encourage swapping constantly. The Energy Transfer Augment could increase the drop chance of energy orbs on kills for a duration after activating Maim and increase the drop chance of health orbs from getting kills for a duration after activating Mend.
This will allow her to run quadruple auras which would be HILARIOUS and very fun! With Duality, that's technically 8 auras. Imagine the madness...
Please DE, I wish for a more active Equinox that utilizes both forms with equity and elegance!
Thank you for all your hard work in the latest update, it's been amazing!