I noticed that the DiMarzio site didn't list the Blaze Custom, so I immediately emailed them about that - I use them in all three 7-string Ibanez that I have.
I was assured that they're not discontinued - there are apparently a number of them not shown currently on the site that are 'current' model - there's a FAQ about that on there somewhere which does list all of their current production pickups, including the Blaze Custom.
Even if they didn't consider it 'current' they would still manufacture one to order for you...
As for using this pickup - all three guitars I have these in are basswood (a '91 UV7BK [yes, with a /perfect/ green colour match - see my web link and go to the pics, you'll see it there...], a '00 RG7-620GN, and a '00 UV777BK).
I went for this pickup in my UV7BK to get more output and more midrange bite as compared to the original Blaze bridge model. This is just what I got - it's a lot like a Dual Sound (6-string pickup, same specs as the Super Distortion) which I use in my 6-strings in these respects. It pushes a nice bit harder, and has a lovely vocal quality to it, being as it does focus a lot on the midrange.
I'll put a link to an audio track, if you want to listen.
Of the two currently in this folder, the one called 'Kotzen track - PODxt' is the one of interest - it was an improvisation recorded with the UV777BK, using the Blaze Custom for a lot of it.
(The other there was done with my Jem777LNG, which uses a Dual Sound in the bridge position, as stated above...)
Click here, and click on the MP3 'Kotzen...'
Hope some or all of the above is of some help.
Needless to say, I am very much behind this particular pickup.