

Only ones that become a challenge is Deathclaws and RadScorpions-in tier 3 x3 block rooms. If you do this properly, most enemies aren't even a real issue anymore. Also, makes them more resilient against radiation damage-they take less of it the higher their End. This directly affects Hit Point gains when they level up. The higher the dwellers Endurance, the better.

And, you do not want to level up rooms to their highest tier (level 3.) So, while your room combo's are level / tier 2 at most, you'll be training dwellers stats up and obtaining better gear. Ideally, you want to keep population level under 25 in the early game. Once you get over a certain number of dwellers in your vault (and they've leveled up a bit) you start getting more difficult enemies. Sounds like you leveled up and built up your vault too quickly.
