It was extremely tight. I probably would have died right as my cds expired, and that wasn't a oneshot at all ;_;
I don't remember the ilvl but I had to go outside on all 3 ground phases, and killed her on the third after the message saying that it was now permanently stuck on the ground, surviving for as long as possible with cds.
The most important part is making sure to doubledip on the ring buffs, in order to get the %crit buff faster. RPPM used to work extremely well with RPPM trinkets and this isn't the case anymore, so it's not surprising that the required ilvl would be higher now. I had permanent full stacks of both Gaze of the Twins and Primordius back then.
In order to doubledip buffs, you have to be preemptively placed where a new ring will spawn. Rings can spawn in fixed positions compared to Alysrazor, and she will usually spawn 3-4 in a row in the same position before switching to a new position, which allows for predicting where the new ones will spawn. The first ring in every flying phase (and after every firestorm) is to the right of Alysrazor, always, then it's random.