in my playtime i opened round about 400 locked crates and i got 2 guns, 2 armor, and 1 arcane pet (glacian).
Dop Rate in Crates for mythics is very low and more lower for arcane stuff.
But also i know ppl getting arcane item after opening just 17 lockeds...its all about chances and luck...

But sometimes its better to farm elite bosses and sell their drops, like the firesquid from Elite Palm Rock...gives good money.
So i bought most of my Gear from others...