Unless specifically designed to be random/ %% (which would be lack of compassion), there has to be a way to improve or increase the reward chances for the skins/hearts. Likewise there may be a method to increase the artifact chances.
Quick example, if I blow up sawtooths, only blasts, no hearts in 10tries. 3 kills farmed twice, 1/2 blast damage, shock and melee down. 1/3 and 2/3 had hearts. Think 50%+ didn't yield.
Boars, three arrows, 2/3-3/4 hp%% in medium range (right when they see you coming up to them) and melee, skin reward. Twice in a row. 3rd didn't yield but 4th made it.
There has to be little things, it will help for HZD2 if we can figure it out now