I have the same thing as Gribnum above. I have gotten multible of all other variaments of 4* gauntlets, chest pieces, and boots, but not a single one of hp%. I have spent 1500-2000 energy on this foolish mission. Im starting to think its bugged.

I won a 4 star uncommon gauntlet with HP percent from stage 12 - 4 of brutal campaign, but the 7.3 artifact challenge was not completed. Any particular reason why? 

Spent about 800 energy for gauntlets...nothing. 

I have spent so much enery and still not dropping the bloody 4* HP% lol

I am thinking if maybe it will have better chances above Hard mode. I have spent +1500 energy only trying this one. At least I use it to level up other champs...

still the same problem in 2022 i cant get the update i got several artifakts with lp% from Arnok heavy and brutal but no update .