After some investigations in loot table, all loot seems to be present. That's why GM's can say there is no problem with loot located on timeless. But, the issue seem located directly in game and almost certain with a script which allow some loot to some class. I noticed after getting
.gm on and spamming opening, the timeless chest was able to loot ONLY plate, mail or cloth depending on my class. But this doesn't work with mobs loot who are giving principally mail and leather. Once again, I'm not 100% sure about that, I talk about my search and experiences, but, it seems dev tried to make like a bad luck protection against class that aren't getting enough gear.
How can I assume to say there is a script with that ? Well, even by changing some parameters in loot table, the same leather loot was spamming. Sure this system is great, but actually it bugs by giving player a lot of leather and mail stuff. Ring, cloak, trinket loot with a low percentage, based on IG experiences with multi characters.
Anymore, I want to say there were no class loot priority on timeless isle on retail, all class were able to loot plate, leather and mail. This was the blizzard directive for gear up faster alts characters.
For resume, if you play a plate or cloth class, you actually can't gear up on timeless like leather and mail class except if you use .gm on and spam big timeless chest or buy some class gear box with 7500 timeless coin.
Hope this will permit to localize the bug faster and found a solution.
I tried to generate a homemade sql solution waiting the next version :
justpaste.it
How to use : Copy-paste it to your sql editor in reference_loot_template table
As this contain duplicate lines, (sorry, missed removing them) maybe you'll get some safe error by executing sql but no stress this is safe.
What happens by using this sql ? : First, all loot table of timeless is correct in DB, so is not server issue. Then, the timeless stuff gear come from multi entries and i noticed all leather loot we drop came from entry 102322. It seems the others entry correctly contains plate and cloth items but these one don't drop (idk why, all seem fine in DB). So, i've just replicated the items entries (plate, cloth and mail) from other entries to 102322 entry. So it's just add some loot to the principal working loot entry on timeless. No more.
For me, it worked, let me know if this worked for you. (you'll maybe need to defeat some rare before you can see the result).
Beware : I'm not a dev, this is a homemade solution and If you don't have issue with loot on timeless don't use this.