torches and annis are more easily farmable
sunders require a dedicated team setup to farm and even then they have much worse distributions than torches, more RNG and chance of failure to find at all, and once you do get them the renewed have way too many permutations, there will be a preference for just 12.5-25% of a combo like +% cold damage / +life / +% fhr.
Annis got spammed because a world event can be triggered to overproduce them, torches can be farmed from grindable components and a solo player can assemble them, and even so the 1/7 warlock variant is that much more expensive.
But now its 30% cold / 30% fire / 20% light / 12% poison / 6% phys / 3% magic. So the most sought-charm being physical right now means only 1/17 of the sunders work with the warlock build unlike 1/7 torches
To really farm sunders you need not just the farmed shards but an 8 player setup, multi loader and hork barb and then its still RNG to find any and I'm not sure what the full game clear expected farm time + odds to find in a single game are
I've been in lots of TZ96 P8 games and grinded a ton and found 2 total. In the same time I could have farted out dozens of torches
A+ for a very thorough and detailed explanation