An easy fix would be… more common and rare weapons. One would think Common weapons would be more… common, but nah, only seven available. Fifteen Rare weapons, if my counting is correct.
Honestly, when was the last time a new Rare weapon was introduced? How about Common?
Some kingdoms lowest tiers are event exclusive meaning that if you failed to get it when it was available, tough luck, you are stuck with Legendary or higher for your mandatory weapon upgrade. Soulforge weapons thankfully sort of fix this issue such as Adana but that’s still Epic at minimum.
Added the other 10 Stars. 
Added what you get for reaching each star.
Also, does anyone know if x3.25 tribute chance gets rounded down or actually x3.25 chance? If it gets rounded then x3.5 would get rounded up to 4 no? That would mean from 14 stars onwards all the way to 20 stars (and beyond to x4.25 at maybe 22 stars) tribute chance won’t actually get any better.
They’ll just Nerf it again when that happens. That’s what they did when 14 stars became attainable.
10% * 3.5 = 35%, not 40%. The rounding you are thinking of happens for pet multipliers applied to small stat bonuses, like 1 magic * 2.75 = 3 magic.