Some quests require players to defeat an unusual number of enemies or an enormous number of enemies (5, 9, 12, etc). Other quests require players to defeat enemies until they find something or a number of things.
The option to fight more than two enemies at a time would greatly speed things along for players confident in their ability to take on greater challenges.
My suggestion to allow players the option to take on three or four enemies at a time in the settings menu.
