Too many people here who doesn't even read into lore comment how "Thrall cheated" because they are on a Thrall hate bandwagon.
People also say that's why the elements abandoned him, because "he cheated!"
No, the elements abandoned Thrall because he used them by force to kill Garrosh. He didn't ask to lend their powers, he just simply took it by force. The elements doesn't give two craps about mortal rituals whether they cheat or not, they just get furious when their powers are being used with force for mere stupid mortal matters.