T3 has been nerfed numerous times, I'm not aware of any nerfs to Archfiend or Zaal however.
Speaking as a US raider, I believe we are the only guild that even does T3.5 atm. If the fights were toned down a bit, there'd be more interest from other guilds I'd guess.
I do agree that the loot should be made more attractive and with a better drop rate. I'd also increase the minor armor pieces that drop.