I, a true gamer, have figured out the winning strategy (solo play):
Once you get to your first tunnel, the enemies can't reach you. Every time you trigger a new room's words, you can just go back camping in the tunnels, enter all words in groups of four, then go kiting until you validate the results. You can find the combination to unlock gateways similarly, and then go onto the next one. Congratulations, now you can play in a still tedious, but safe way.
Note to the dev: Mastermind punishes the player with each bad guess, because they have limited space on the board. If you take away the punishment, you take away the challenge.