the whole you have to run X amount of test with deca is bro science at its worst.
the reason for deca dick is PROGESTERONE. running test with deca DOES NOT block progesterone.. it will coat the problem giving the impression that it is helping but when you come off the bad news will come in a big way.
if you are gonna run a nandrolone you should run anti-prolactin with a very good AI. and even that may not solve your progesterone issues. if you choose to run deca or NPP you better have a solid pct lined up that is lengthy .. cause i promise you your LH will not rebound for a while due to elevated progesterone. i find it funny that the few guys that rave about deca are guys that go on HRT at 28 years old. does anyone see a connection there?