Even with two human players this is not possible. Not at our skill level. It is part of the gate for the upgrade to our 120 class spells. Any advice, besides "try harder"?
Monopoly of Souls (or the equivalent on the Baron, the name escapes me at the moment) is VERY slow casting. You have a lot of time to get the Cat's eye off. What makes it tricky though is you have to be targeting her when you cast it, and if you are off doing Trade Route Flags, it can be easy to miss. I added an ACT trigger just to make sure I didn't miss the text. When I hear the audio, I stop everything target her, and cast the agate. There is an alternative as well. Don't worry about it at all. bring a healer merc. Let them rez you when you don't cast it in time. This method also resets the trade route stone skin.
ACT Should not be required to complete a solo quest. We did see when she was casting and did attempt to interrupt it, however cat's eye takes too long and she finishes casting before it takes effect. The mobs also repop, so it makes it harder to target her. Certainly not quickly. She is casting it too fast or the death prevent is casting too slow. Even with our best, it's not enough. So you can say we are fail players, but I can assure you I will never be able to complete this. That would be fine if it was some side quest that just gave me achievement. I'd skip it and move on. But something important is gated by completing this instance.
Don’t have any issues making this a quicker cast for solo. Will add it to the list but I’m afraid it probably won’t make it into game till an update after next week.
To be clear you don't need ACT. It has a cast bar and a message in chat when to use it. Also, the next time to use it isn't until it becomes clickable again. So if you watch the agate after your first use you will have a decent gauge when the next one is due. It comes probably 10-15s after it becomes clickable again.
You asked for advice. ACT is not required, just helpful. I completed this several times before creating the trigger so it isn't anywhere close to impossible. I'm not an elite player by any means, probably middle of the curve. I just made it easier with ACT. Sounds like you don't have or don't want to use that, which is certainly your prerogative. All you need to do is look for when she says "I trade in souls" or the emote that says the Cat's Eye Agate begins to glow. With two human players you should be able to catch that right away even if one person is off doing the trade route. Other options are to create a macro that will target her, cancel spell cast, and use the agate. This may save you enough time if you are close. The option with the merc will still also work. The merc does not die like a regular player does when monopoly of souls completes. The merc can then rez you and you can finish. I'm not sure what server you play on, but if its Skyfire, and I'm on, I can also help you with this. So if you don't want to wait for Chrol's fix, you do have some other options to get this done.
Trigger the Cat's Eye whenever you see: "Cat's Eye Agate begins to glow" "I trade in souls" "What's a soul to ye?" For those who DO use ACT: <Trigger R="Cat's Eye Agate begins to glow" SD="Use Cat's Eye" ST="3" CR="T" C="Fordel Midst: Bizarre Bazaar [Solo]" T="F" TN="" Ta="F" /><Trigger R="I trade in souls" SD="Cat's Eye" ST="3" CR="F" C="Fordel Midst: Bizarre Bazaar [Solo]" T="F" TN="" Ta="F" /><Trigger R="What's a soul to ye?" SD="Use Cat's Eye" ST="3" CR="F" C="Fordel Midst: Bizarre Bazaar [Solo]" T="F" TN="" Ta="F" />
