I was reading this thread the other day, it might help a bit: Guide: Recommended stats for end game
For me, the main campaign is pretty straight forward, but I’m pretty new to Crucible / Shattered Realm, and that introduced a whole new level of difficulty and challenge.
That being said, there are general principles that apply to the game as a whole. Some, however, are perhaps more relevant to endgame content. I recently learned to appreciate the importance of armor as a stat after getting my ass kicked by certain monsters in SR (my Purifier gets his ass kicked by late-stage SR Reaper of the Lost but my Tactician, with natural Soldier/Inq armour/phys resist boosts, kicks HIS ass).
Overall, I’d describe the game as a kind of balancing act between offense and defense. But, since there are more than two factors to each of those elements, it can get complicated and come down to narrow margins. Basically you want to boost DPS as much as possible, whilst retaining good health, max resists, and having some form of healing (ADctH and/or healing skills) and damage absorbs (flat absorb and/or % absorb and/or good armor). Compromise too much on either element and suffer. Achieve both and succeed (and I reckon the essence of the best builds is that they EXCEL in both).
But this leads to the obvious problem of equips. You do need good equips to achieve all this. Luckily GD has a fairly generous drop system. Bosses and totems along the way usually provide something serviceable, whether in the short or long term.
I’d say you want to have a kind of “pilot” build that can complete main campaign without difficulty (and without TOP tier gears) and then can run deep into Crucible/SR to help farm some more equips. For me, that character was Tactician, backed up by Druid. I was pretty lucky though to have a couple Havoc guns laying about from Vanilla GD days which I put to use on the former (obviously I’ve upgraded to mythical now). Good lower level purples and a solid build will help tremendously.
Perhaps let us know exactly where you are at on the game and we can assist more specifically?