📜Rate increase scrolls - this is important. 
How rate bonuses work using drop as an example:

 - Base rates: x3 (300%) 
 - From 50 sets: +2.0 (+200%) 
 - From scroll: ×1.35 (+35% to current) 
 - From aura: ×1.10 (+10% to current) 
 - From premium: ×1.5 (+50% to TOTAL)

 Formula: 
 ((3.0 + 2.0) × 1.35 × 1.10) × 1.5 = 11.1375 
 Without premium: 
 (3.0 + 2.0) × 1.35 × 1.10 = 7.425x 
 With premium +50%: 
 7.425 × 1.5 = 11.1375x  
Passive skills from costumes, dwarf mastery abilities work similarly to scrolls, they multiply your rates.