Haven't noticed any changes in tier-up rates lately.
Btw, it seems not only each item type but also every single
item has it's own unique tiering-up rate variable.
Meaning, if a certain gun has, say, 103 @ tier 4, then
Code:
actual tiering up speed = x * 103
where
x is unique for every single item.
It is very hard to prove with UL items, but relatively easy with L items.
Have burned through bunch of full TT CB19 lately, some will break before reaching T2, most somewhere around T3, yesterday i got one that reached T4.2 already at 85% TT remaining (in average, every 3rd shot an incremental tier-up). All (L) guns are tiering up very fast (compared to UL), several tier-up messages at once is not uncommon, but this one is a real "tiering champion". If it keeps going at the same speed it will reach T10 before i have used up half TT.
There's another way to explain the difference between different items of the same type - a "timeframe theory".
Suppose there's certain times that increase the chance to get an (incremental) tier-up, and other times when it's less likely. To find it out, i stopped using that gun yesterday, and if the incessant flow of tier-up messages will continue today it's most likely not about time, then it must be the unique variable of that certain item.
