Drawing using PDI from FViewportClient::Draw/FEdMode::Render - Limitations?

I have an editor plugin in which I draw some primitives using FDynamicMeshBuilder. It’s fairly simple and frequently changing, so it makes more sense to just draw within the overrides mentioned rather than set up a dedicated primitive component and scene proxy. I’m just wondering however if there are some limitations when using the PDI in this context?

I am seeing some issues with translucency, z-buffer and lighting. It’s as if the order in which I make successive PDI calls is affecting the rendering order, regardless of scene depth. Also, lit materials are just coming out black.
I believe these issues only started to show up in a recent engine update, either 4.13 or 4.14. Anyone have any ideas why this might be?