Since it seems that the Devs are not going to increase the radiants drop rate in another depths ..... well , here is a very simple solution that should solve everything ( atleast until a bigger change come ).
Well its very simple , just make the danger missions start at depth 26 for vanguards , this way the treasure room will be at depth 28 , and this room contains alot of red boxes so , yeah maybe like 30 rads per danger mission run .
Not the perfect but it shall solve the problem , its better than "from 0 to 9" per one vana run .
PS. if you are not a vanguard yet the danger mission will start at 24 ( if you are more a champion or higher ).
"Who are you to be modding around here?"
Well, there would be no point in having two of the exact same levels in the same stratum. It's like having to decide between two bowls of salad, or two plates of french fries, and one of them is bigger. Of course you would want the bigger plate, am I right? Nobody would want the smaller plate.
"What do you mean by three?"
Theree are the T2 DMs and the T3 DMs. Depending if you are T2 or T3, you get sent to the respective teir (none for T1 though).
"It could work like the T2 and T3 seperating model."
Like I said before, there would be no point in having two T3 DMs for each different DM. It would be much easier to raise the depth by two than to make a new level that seperates players more.
If you have the current T3 DMs' depths raised up by two, then I'll give you your +1.