Just a bit of adding clarity on this as it was changed.
There is NOT a NEW 100 levels to grind though the grind is technically the same.
Tier 1: 1-89
Tier 2: 90 179
Tier 3: 180 - 299
Tier 4: 299-300 repeat over and over. You do not level to up any more but repeat the same level over and over.
BW mentioned something "different" about tier 5 (and that information was also datamined) so it might not be in galactic command at all. If I can find that quote I'll list it.
This is some of the posting about the changes coming. A bit like 4.0 so better than what it was if you run OPS.
http://www.swtor.com/community/showt...64#edit9253564
Around April 10 there is a new daily grind area and probably rep grind with it combined with a extremely small Iokath story. There is only ONE boss in the new OPS as bw is unable to do more than that. It seems the rest of the OPS will come out one boss at a time every 2 months and wont be complete till December 2017.
I really do think swtor is in a bad place right now given what 5.0 did and how it drove off so many gamers with the very RNG you're talking about and so little new content. SO I can definitely see where doing only the class stories and getting out is a preferred way to play. Most stories after the class ones just aren't worth mentioning.