Warpstone Flux Rating: ⭐️⭐️⭐️ (ish).3/5 stars. Totally Playable, but you're probably not going to take him unless you are running an army based on deep striking (or are facing off against an opponent you know will use the same). The Ld re-rolling can be strong in the right situation. The BS bonus is good. Also needs a FAQ in my opinion...
In second edition, the Master of Signals is described as those marines who maintain a vital link between front line and support for the legion. They are also described as being able to call in support strikes from distant batteries and orbiting vessels - much like in first edition - but sadly the rules no longer reflect that as I don't see any orbital bombardment rules next to their name any longer.
Re-rolling morale and pinning checks using the Master's Ld (or any other model with him) once per turn is neat. Re-rolling reserves is good as well. The cognis-signum is nice for the bonus BS too.
Instant death. Loss of utility for orbital bombardment compared to first edition. Confused rules between supporting Deep Strike, and opposing it. Playable either way, but annoying.
Difference to First Edition:
Worse. This character is massively, massively diminished by no longer having orbital bombardment in the rules. I am very sad about this. Perhaps it is just an oversight given what is written in the background. I hope to see this FAQ'ed.
Master of Signals, Charnabal Weapon (105 points).
The Charnabal weapon here is to take advantage of the higher initiative of the Master should he get into combat -- which is very likely since you will be (or should be) running him in the same squad as a praetor in all probability. Take a jump pack if required to keep up with other characters. Gift bonus BS as needed.
Master of Signals, Nemesis Bolter (105 points).
I have mentioned before that I think we will see many Nemesis Bolters in second edition. This is a back line HQ who tries to not make himself too much of a target and can use his Ld to aid the army. Gift that bonus BS by attaching to a heavy support squad.