I think the puzzle would be fine with the following changes:
1. No instadeath. Taking the wrong teleport instead sends you back to the first room, but spawns a few Flesh Spawn in each of the rooms visited so far.
2. When the proper teleport is used, the invalid ones close somehow (sector color change to dull gray, and they stop working).
3. Less opposition in the room. They are pretty cramped, so having to fight off three hell knights or a cybruiser is seriously overkill. It's pretty much impossible to avoid taking damage. Lower the strength of the opposition, or increase the size of the rooms so that there is some room to maneuver.
The length of the sequence could also be decreased a bit. Remove two or three rooms. Keep it from becoming tedious.
For extra credits: make it so that taking the sequence in reverse is possible (no instadeath), but doesn't "validate" the rooms as I suggested in 2. At the end of the sequence, the player is sent to a secret area with a megasphere or some other sort of goodies.