Wow you really are unlucky. I guess this means I am extremely lucky to get an eternal pet so early as a player. At that time,I used eternalized but I didn't even have max farming affixes at the time and I was a newbie too. I still haven't found another eternal pet though ever since I got fully maxed farming affixes.
My first ever eternal pet is a bane pet with deadly strike with quite cool affixes. Still wish I could get so many more eternal pets. On the plus side though, I got two eternal maps. One of them I completely lost and another one safe in my stasb and not being destroyed by my inventory bug which makes it exactly the same as my hirlings inventory and destroys everything and replacing them with an exact carbon copy of a hirling inventory.
Anyway, how active of a player are you? That enslaver feat plus tons of grinding and more. At least the ascensions can make it somewhat easier because treasured increase eternals/crystal legends by 200% which can be added onto the eternalized or crystalline; accomplished reduces the numbers needed to complete a feat by 25% and rounded up to whole number which explains why I defeat a mythic enemy everyday ;and ultimately, it makes enslavers feat so much easier. Fortunate is great in overall farming along with dealer and accomplished with treasured as you already know. Hunter and enshrined are extremely useful too.
I commend you for really grinding hard to try and get an eternal pet. Unfortunately, its been months and I still haven't got a second eternal pet. What really helps is rapidly finishing floors though. I got my eternal pet without even trying which is extremely lucky as well.
Speed=power and knowledge= power and speed increases chance to get crystal/mythstone/legends/pets and anything else and you learn quicker because your gaining stuff quicker which makes the knowledge= "power and even more power with more knowledge" completely true.
It really does help to be quick and active. Every game rewards activity alot more than less activity. This game is so good and will always get better with each patch. Grinding can be grueling but thats with any game. With this game, at least it's fair because its not PTW (pay to win) except with the miniscule 52 cent offer but thats probably not too much Also it is optional to not pay for hirling as you already know. One other thing a game likes rewarding is the speed you get things + the activity of gameplay.
Thanks for reading :). Hope that wasn't TL:DR
If TL:DR; I commend you for your efforts and understand your pain.