well r2-r3 withering touch is all about preference..for example I keep only r2 with 66% chance for pve since its better than before with r3 and 45% chance..on single target r3 is useless for sure but we can doubt about r3 on aoe since. If its just 3-4 mob pack u can either decomposotion all mobs or just 2-3 while trusting the chance of neuro triggering on others. If its more mobs then it means the pack will die very fast since its how astral was always built.
Summoning mastery is also choice of preference, it all just depends if your pet actually dies/or if it dies more often than each 2 mins(that shouldnt happen most of the times in this new astral) so yea you can totally skip it or choose between r2-r3
I have doubts about triggering timings more than chances.
I tried especially in astral many times and always same thing happened. I mean 15-20 second pack fights and r2 spends first 5 second for nothing. Still like i said its about playing style and preferrable.
Personally, summoning mastery is a waste of ruby in pve also in pvp(if u have a perma dod maybe usable). Especially for pve i prefer to renew my dots and resummon the pet if its a long fight and if we are at the very begining of the fight. Plus, with dak touch we already have two pets..