They are prominent, they just lack any body/weight to them. I had 2 masya’s both the same. I value the fullness and lush texture of vocals and masyas vocals are just clear.That’s weird about your Masya’s because Masya is a vocal bud. They should be the most prominent thing in the sound spectrum. Have you tried reversing the inputs to make sure they are in the correct way? You never know if things are wired correctly...your ears will tell you....or a multimeter.
I use it for instrumental stuff but honestly I don’t like it for vocals at all.
I tried the wires both ways, even reversed the pins on one but the sound was out of phase.