Interesting. I did that recently on a new character and didn't have that result.
Number of beetles scales with difficulty, not player level. Low-DEX non-psi builds with crafting can easily make a stealth set that will get them past the beetles, since psi beetles have very low detection. Without crafting, and without stealth, you'd need to show up with several traps and grenades. If you had an adrenaline, that would be even better, since you could open doors, throw grenade, and close doors all in one turn. Incendiaries work well there, since as long as you open and close the doors on your turn so the beetles see you, they'll keep crowding around the door, even if they have to stand in fire to do it.
