InDesign Gradients Showing a lot of Gray

Right now, I'm trying to create a radial gradient for a client who uses Pantone 282 and Pantone 5415 (Navy Blue and a sort of Slate Blue). The problem is, I'm getting this ugly-as-sin gray taking up a large portion of the transition space.

Why? And how can I fix that?

I have read a couple of articles from Google searches, but they always seem to terminate in a black stop and the solution is to "add richness to the black". These are going to be print pieces used in a variety of media and I would like to stick with the Pantone or at very least CMYK values when working.

I'm looking for a smoother blue-to-blue transition, like this (I achieved this by playing around and setting both stop colours to LAB):