Re: Pickups for ibanez RG5EX1
My main axe is an Ibanez RG5EX1. I don't play death metal, I play hard rock, but the levels of distortion I run are probably more similar to yours than they are to classic Rock 'n Roll or blues. One thing you haven't mentioned is what amplifier you play through, which can have just as much if not more effect on your tone than the pickups in the guitar. A pickup that sounds awesome through one amp may sound horrid when played through another.
That said, I run a JB8 (JB with an AlNiCo 8 magnet swapped for the stock AlNiCo 5) in the bridge of my RG5EX1. From the reading I've done here, I understand it should sound similar to the Duncan Distortion, but not as bright in the highs. I am very pleased with the sound of my JB8, it has plenty of mids which allow it to fit into a live mix without too much trouble. The other guitarist in my band runs his guitars through a Marshall w/ dimed mids, and I'm able to hold my own in the mix with my amps mids set a little more than half-way. Since modern heavy metal tones tend to have a less mids than hard rock tones, IMO, the ample mids of a JB8 may or may not be to your liking, and you may perfer a Duncan Distortion instead. FWIW, the JB and DD share the same coil winding, but have different magnets (A5 vs ceramic).
I also have another Ibanez RG*EX* axe that I have a Full Shred in. I have a love/hate relationship with the pickup. To quote uOpt's excellent description of the FS:
The FS is entirely different. It doesn't get rounded off by the PAF-like polepieces that DC and DD have. The hex poles make it very "assertive", forward, reacts stronger to playing nuances - but not neccessarily in a a good way, it can lack body. More of a high-gain soloing pickup. More dynamic than the DC and DD which have ceramic magnets that compress.
On one hand, I love the forward, articulate nature of the FS and the fact that it doesn't mush out or become indistinct under a lot of distortion. On the other hand, I hate the fact that it is a brutally honest pickup that won't let me hide my mistakes, and that I don't yet have the chops needed to make it sound good.
Hope that helps.