I don't know how it compares with the Cosmic Dungeon (haven't done that one yet), but the Frozen Wasteland is a decent choice. The T3 Evo Runes are still pretty rare, but you'll get plenty of T1/2 along the way. This is what I got from 100 runs in both Hard and Madness:
While 100 runs isn't a huge amount, and I wouldn't put too much faith in the reliability of these results showing similar numbers for the 1* T3s, it's enough to give an ok idea of rough patterns. Madness costs twice as much SoT to run, but on average drops a little over twice as much as Hard. So up to you which way you want to go. Can read a little more about that dungeon here if you're not familiar with it.
Azagthor-0732