I got 4 x 3* red evo shards Today. At Dungeon level 10. I have spent 3,5 full sands of time. Its approximetely drops 1 3* coloured shard for one SoT on level 10s in general. I can't even imagine how is it at level 7 or 8..
Btw, does anyone get rare souls from dungeons? I never got after update. It was raining on level 10s before.. Its tough to being depended on trooper points..