This has probably been posted before, and some of this will probably already be old news, but I just got done this, and it was not easy in the slightest, and I thought I'd share some tips or subtleties about how to overcome the struggle.
Talents
TM
AG
EgT
EleB
LMT
LR
Phase One
Pre-Pull how you would any raid boss (ie prepot, fire ele, EleB) FS her then drop LMT immediately. I didn't want to waste any time CL'ing the wildcard imps so I didn't LB into a FS to refresh; I nuked the wildcard first. Now what I changed in the last ~5-10 attempts was not grab toteming the burst imp and the heal imps. I gave myself enough space to where I could pop SK and nuke the three down before the burst imp could get to me. I literally can not stress enough how much easier it was handling P1 doing this
This fight is literally "if you fall behind, you die" spare a very rare SO/CLO scenario where you might recover, I didn't have the leggies for making mistakes, so any room I could buy myself was valuable. I found that if LB was overloading a bit, I could throw out a ES before saving up for her shield, but I would gauge that for yourself and see how the run is going.
If SK CL gave you any kind of overloading during the first set of healer imps, after her shield drops, she should be around >60%, 65 would be the cut off point imo, if I couldn't get her to phase change before or during the second healer imps spawned, I'd wipe and try again. The wildcard imps should've already spawned at this point, drop LMT and CL her to push the phase, Earthgrab or bind to delay the healers.
Phase Two
After that life changing strat of SK CL and saving the hassle of trying to root/manage add placement, phase one became infinitely easier, and phase two was really hit or miss. If you managed to make the healer imps spawn BEFORE she translocates, bless up brothers and sisters, because that could very well be the pull you get it. Managing the slow/root was the hardest part about the first teleport, because if you're standing on the sides of the platform for the burst imp placement, then trying to throw in that root before the healers get to Agatha usually spells death if boulder RNG is lame. Always save LMT for the wildcard, as it trivializes them; extra points if she shields because it actually makes breaking it pretty accessible with (usually) just a fully loaded ES. Now, this is where Ancestral Guidance saved my kill, when you're at ~30% hp and healer imps just showed up on top of a wildcard at the ass end of her second phase, things can look pretty bleak. This is where AG with SK can, quite literally, heal you to full in a GCD, and not only that, if the Overload is strong enough, can cause her to teleport again. With my lack of the legendaries, I don't think I could've done it without AG honestly, and I'd label it a must pick for this fight. You should be paying attention to the burst imp placement and boulders anyways to warrant not using gust of wind.
Final 30%
When she teles the third time, this is some real shit. If you've been managing your slow/stun, then you have 4-6+ healing imps begging to get to her. Lust immediately when in range, pop your second potion, earth ele, everything. Fire Ele wasn't up for me but this was good in my situation, as I was able to summon it on the 4th/5th teleport and secure the kill.
Honestly theres no sugar coating it, it was a really rough time, spending hours trying to figure out different talents or strats. If you don't have sephuz, make sure to run the Spiced Wildfowl Omelet for the clutch movement speed. Also the kill I got her on, I ran out of augment runes, but it definitely doesn't hurt to have them.
Ascendance build with PoT is still pretty good, and I would recommend popping Asc after you SK CL the first heal/burst imp wave. Belt is a bonus.
EQ becomes even more valuable then it already is on this fight if you have the boot/shoulder combo, and should play it out how you already play it in raids.
Other than that, good luck, you're gonna need it.