on-chip data recovery topic

Hi fellow xda-members,

I've already posted this in the One XL section, but I realized it is a more generic problem/more generic technical question.
Thats why I post this again to maybe reach the real experienced guys from xda whom maybe know an answer to my specific question.
Ive summarized the most important points to not double-post the question.

I recently wiped my One XL 32GB with the HBOOT Factory Reset,
didnt know that it wipes the internal storage aswell...

Needless to say that I work with the phone and the data is priceless...

I already piped the whole block device(mmcblk0) via netcat and dd,
opened it with a hex editor and found out the whole fat-partition is nulled.

From what I know and heard, the only way to really secure delete any storage device
is to overwrite the data several(Mostly heared 7 times) times to avoid unwanted recovery.

The Partition wasnt formatted and neither mounted yet, there should be no changes made from android since the wipe.

If you take that into account, there's a hope to recover the data.

Does someone have experience with jtag raw data recovery?
Is there any way to gather other/deeper data with jtag?

Thanks for all replys

criestr