This is definitely the most challenging of the achievements out there. None of the other Gauntlet tasks even come close.
That being said, I have been tracking my progress with it in another thread using the Snowloon/Thrasher duo. I didn't have luck with any other combo despite sticking some out for months. So far, I have managed 46 encounters since 5/31/24. I'm almost half way there and am averaging about 10 a month or 1 every three days. I managed some INSANE lucky streaks where I got 3-4 a day so it's really just RNG.
I know this one is challenging and at times mind numbing. I'm honestly driven to get as much done before they add more families to the Gauntlet, thus making it harder in the future. Right now, it's a slow, but it's only going to get worse. I'm sure the devs are hesitant to make it so that only one companion is required to be on the opposing team simply because it would allow us to then progress too fast. I see tons of Snowloons and Thrashers every day. I could probably knock it all out in under a week if they changed it.
But I also understand how frustrating this particular achievement is for the vast majority of the site, so I think that if enough people are struggling with it or just avoiding it altogether, something definitely needs to change. Like, even if I've been toiling and busting my furry behind to knock it out, I won't lose sleep over it being made easier for everyone later on.
EDIT: I just saw someone mention having the total successes reduced and I feel like that would probably be the most fair compromise!