Does your armor tier up only when it gets hit and absorbs damage? If you hunt in armor, does it tier up faster than when you sweat in it? Does it tier up faster if you get hit by bigger mobs?
As far as I can tell, each time and armour part absorbs damage it has a chance to tier. But thats just from personal experience. Every time I have had a tier event it has been at the same time as taking damage. One way to check this would be to see if harness was generally at a higher tier lvl than other parts as it gets hit aprox 24-25% of the time. Can't really comment on impact of mob maturity or damage amount.
I can say my armor tiers up more often when hunting mobs that hit me more often, such as Owekos. But I do have armor tier when getting hit by Combibos while swunting on Calypso.
Items tier up each time they are used and armour gets 'used' when something hits it. So a creature that attacks quickly and hits often will offer more chances for your armour to tier up. I don't know if the difficulty of the creature (or weapon, for PvP) used in the attack makes a difference, though I wouldn't think it mattered. - Deathifier
Ok, thanks, I'll make some tests to figure out if the amount of damage an armor piece absorbs matters.