The best way to win against 2-3 enemies is to put 2-3 enemies in your active followers to fight them. If you only have your starter follower to field, convert one of the enemies (the most powerful or most useful for your team) - then not only will you have one less enemy to fight, but when the battle is over, you'll have a new follower to field.
key [1] bullet [2] rocket [3] laser