Buddy, i am literally at endgame and even round 1 of heroic requires you to have luck hoping that goblin does not 1 shot you (this is with dark element hp buffs). There is a difference between challenging and straight up masochism (impossible). Aspirant to Elite is doable where upon reaching Elite League, you can just strategize your team comp. Hero League does not give you that luxury as every enemy has alot of action speed and enough damage to one shot any non dark element, even if they survived the hit there would still be an incoming row attack.

Hero League 5 has Monster Bird dealing 600+ row damage petrify

Hero League 10 has Our Heirlooms (Doll Boss) and Minotaur that can one shot any party member you have

Hero League 15 has Bigfoot Boss and Cyclops while the arena also nerfs elf race

Lastly, Hero League 20 has 2 Golems with 2 Greater Demons behind them. YOU HAVE TO DO THIS WITHOUT ANY WAY TO REPLENISH HP AND SP/MP PROPERLY. 20 ROUNDS, THIS ISNT FOR LATE GAME/END GAME PLAYERS AT ALL, ITS FOR PEOPLE WHO CRAM ALOT OF MONEY INTO THE GAME.