Which ones have you tried? Ash is supposed to be on the brighter side, meaning you may want to find humbuckers that have more bass/mids.
I just put a Dimarzio Tone Zone in a guitar with a Paulownia body (supposed to sound like ash) and maple fretboard neck. Absolutely crushing sounding.
I can't comment on the Wenge neck, but my Ash bodied/ maple neck G&L Legacy sounds pretty awesome with a WLH bridge. Nice thick sounded rhythm with good detail and singing leads, I want another for my Tyler.
I would try to find things that would have an eq curve more like a p90. I would avoid bright pickups, and low wind PAF style stuff.
Which ones have you tried? Ash is supposed to be on the brighter side, meaning you may want to find humbuckers that have more bass/mids.
...put a Dimarzio Tone Zone...
The stock Legacy came with JB correct? You did not like it?
Anyways it seem like most ash guitar is paired with maple fretboard/necks.
This - only I would go with an Air Zone which is a Tone Zone with some tiny spacers on the magnet that airs out the presence overall making it a little smoother. You can still grind with it but it's more agreeable with ash and I know this because I have a vintage stratocaster rerouted for humbuckers with an Air Zone installed. It's one of my favorite sounding guitars.
Usually you're relying on the amp for the type of music you're playing. I've been able to get death metal tones out of low output pickups.The main thing you're looking for is to balance the sound of the guitar itself. The bridge is going to be the position that gives you the most treble, so it's no surprise that a brighter guitar may have some annoying overtones with brighter pickups.
One of the thicker sounding Dimarzios like the Air Zone (basically a lower output Tone Zone), Air Norton, Gravity Storm, or AT-1 or either of the Breed models (neck or bridge) should work. You can also try the Duncan PATB-1 or PATB-3, which are made to thicken up the sound of thinner/brighter guitars.
Which is why I posted this two nights ago: