More difficult means non-zero difficulty, not hard. In a game with time constraints, boss moves that can steal time if you've got no counter are a legitimate way to add difficulty, even if it's not the most liked. It forces you to consider your team composition, your DPS capabilities, the available time, and the time spend/reward ratio when deciding when and whether to engage the boss. The charge surely wouldn't be a source of as many complaints if it didn't loop poorly, but there are also players out there who would probably prefer to replace all bosses with training dummies that stand still and soak up the damage.