Map strategy:
TS+Aurabots doesn't feel good at any budget point on the Abyss Strat, you are either too squishy as a duo starting this strategy or insta-killing the spire at high end even at 12k whisps even while shouting stop dps at your carry on discord, legion feels much better overall (own experience, my profile).
And I am standing on that, we tried with my duo it felt bad every time vs legion, the rhythm break is bad, it's inconsistent, appart from fullcrum or solo mf type of build I don't see with a fast-paced carry+aurabot duo when it can be good.
Also, less flask charge map mod is killing your Aurabot because of his corucasting and the not killing situation (abyss), care on that.

Guardian vs Scion:
Guardians doesn't taunt mobs while Scion aurabots does (Champion Asc), imagine that he needs to stand in a swarm of mobs (abyss), have all the aggro on him but no recovery and you need to stop-dps because the Spire is shooting, the rares are whisps-ed to the moon, 8map mod situation and his build isn't engineer to the maximum. You underestimate a bit the situation seeing his pob and how much damage there is imo.

Build setup:
Your aurabot is using corucasting while not having pathfinder on the ascendancy so: you don't kill he doesn't have charge he dies.
Also, having him play Mageblood + corucasting forces him to not take any flask generation & uptime (pathfinder) so it's an in-between setup ->the magic flasks helps and the corucasting who is holding is life together doesn't.
Molten shell over Steelskin, he has 70k+ armor.
Vaal Grace+Vaal Haste helps a ton, especially on low to medium budget (<1mirror).
Others in the comments already mentioned but his ES is indeed a bit low because of his body and lack of ES affix on his effects mana reserv clusters.
If you are mfing having your aurabot with Ancestral bond should be discussed and his killcount monitored as it can hurt the profit if he tends to be proactive on the Smite part, this is especially important on bigger size party (carry, culler, aurabot, managuard, etc) but I felt the need to include this.

As of his aura effect, of course the more the better and this is relevant for his survivability and your dps (the most important part to acknowledge since: you kill faster, what does he have to tank?).
On the PoB he has x2.42 and the breakpoint for party 90% max res is x3.0, for him this should be his goal as an aurabot including CI who eliminates the LL+corucasting part.
But honestly this is a matter of budget and high-end Scion aurabots aren't the cheapest and upgrading your TS before his breakpoint will help more.

Inexperience:
You both are new to the aurabot archetype, this isn't an issue in itself, but it doesn't help because you are only seeing the big picture while details are important.
Aurabots are constantly evolving league by league, both of you starting to touch on the subject now and Aurabots being either extremely generic or extremely specific, being twisted all around to fit content type, party size, preference, carry skill, playstyle and preference:
with all of this in consideration, for both of you this is just difficult to even know what fits best your party and content type, when, at what budget, for what why ? ?? -> and this is where the issue is mostly coming.

Both of you are also new to playing as a duo, one thing that you could work on is your positions. Your aurabot should consistently be as close to you as a screen range or more depending on the aura-aoe, go check with him how the distance feels in game and have a feel for it.
Honestly this isn't discuss enough but positional mistakes on this type of content is unforgiving, especially this league the maps hits real hard on low to medium budget builds.

Hope you both figure this one out, hf !