but TFB NiM and S&V NiM were not released until a good bit AFTER Makeb.
RotHC was released April 9th, 2013.
TfB NiM was released June 12, 2013.
S&V NiM was released July 10, 2013.
So both modes were released within 3 months of Makeb, while DF and DP are having to wait 6 and 8 months, respectively, for their NiM modes. So if you think that Bioware has been releasing content at too quick a pace, it seems that Bioware agrees with you.
As for the rest of your post, I certainly agree that shadow/assassin DPS could use some love, particularly in the utility area. Letting the phase walk of a shadow DPS buff damage dealt by 2% for anyone standing inside it would be a nice buff to include with the new expansion and level cap increase.