Since there is a whole set of them they are only listed on the U37 page instead of like 20 individual pages. Means they don't show up on individual weapon searches though.
For me, I have TF T0 (for ML22), TF T1 (for ML24), and just now I'm getting into LGS (for ML26). Ravenloft raid weapons are 28, otherwise Morninglord etc are 29. If you own it, 2 runs of LShroud should get you a T2 LGS weapon if you ask for Small/Medium ingredients (only need a few people to pass to have enough ingredients, and many will happily), which is pretty great.
It's worth having multiple weapons if you plan on ETRing (or even just epic leveling) frequently
the powerspikes are pretty noticeable.
AFAIK Volley is BIS among GXBow builds; excellent base damage and the fact that it's Bludgeoning damage (and thus qualifies for Pulverizer in LD = +1 crit range) mean it wins DPS wars, and Fetters + the guaranteed 90% slow proc is amazing utility as well. Besides, it takes a max of 20 Baba runs (15 if you run on LH like most groups do) to get the runes for it (if it doesn't drop), whereas Archon's can be a pain to farm in my experience.
As far as Armorpiercing for a ranged build, I think your best bets will be either
Legendary Mask of the Vulkoorim from Toxic Treatment (if you own it), or a Cannith Crafted Gloves/Trinket (only level 50 for the AP shard, but the ML shard is a lot higher for an epic piece...). Otherwise you're using an entire gearslot for one effect like
Legendary Pendant of the Warrior's Focus, which feels bad; or requiring raid loot like
Molten Silver Gauntlets which isn't much better (although if you plan on melee lives in the future consider getting a pair). Still, Precision/Grim Precision/Opportunist/Airship/whatever gear you can use adds up fast.
Edit: to address your edit, Cannith Crafted ML34 is only +23. But you can put like Doubleshot, or Bluff, etc on them as well