Background
I am DMing for a group of brand new players who come into D&D without really much of any role-playing experience, even as far as video games. The group is small with 3 players; A Forest Circle Druid, a Beastmaster Ranger who likes to get into melee, and a War Domain Cleric.
We are running through the "Lost Mines of Phandelver" campaign to start with. I am new at DMing myself. We play without maps or tokens, mostly because I work 55 hour weeks and don't have a lot of time to make maps. The party is currently level 2 and so far I haven't been making any changes to the combat encounters.
The Issue
Some encounters are starting to follow a pattern where the enemies come at the players, who are basically standing side-by-side. The number of enemies tends to be about four, and so on their turn they move into attack range in (almost) a 1-on-1 face-off with one player character facing two enemies. Then there is a boring brawling match where each player or the enemies roll to hit, roll damage, and repeat. The player who beats their enemy first moves on to help a teammate, until they win the battle.
The players do use spells at the start of the battle to quickly take out one or two enemies before the bash-match, but don't want to use too many resources too quickly (a concern that is well-founded)
This happened once before, and I wrote it off as something that will get better, but on our last session it happened again and I was suddenly very aware that the players were bored as the combat dragged on while everybody was getting poor attack rolls. I tried to make the enemies change tactics, by grappling and shoving, which slightly mitigated the effect but was too little and too late to turn the overall battle into a good experience.
Question
While at least roughly following the starter campaign encounter concepts, how can I keep combat from becoming a boring brawling match for this party?
