Then run up to them, catch them by surprise so you get a free turn to close the distance, there are options but it is tactically oriented. Also turn down the difficulty is an option, nothing lost by playing on an easier difficulty. If you're in range with a melee character they should get a reaction when an enemy runs away which gives basically a free attack action. I haven't progressed far but it feels like an expected difficulty at normal. Not saying normal is easy but you're only expected to do a few encounters before resting so your casters can perform well.