Regarding resolve stacking help

So I'm playing S14 after having last played in S3, evidently the game has changed drastically.

I would like to know if I'm getting everything there is to get regarding resolve stacking.

You basically max out resolve stacks to gain insane amounts of armor which contributes to your damage (from paragon node) and also when you stand in fortress after you get the passive that grants X amount of damage per resolve stack.

So basically, if you do not take fortress, you lose out on that huge multiplicative bonus, but, you at least still can get a good chunk from the paragon node.

I am planning to use arbiter of justice with the 5 set charm that gives all ultimates. Am I right to say that you won't get the passive upgrade but only the base ultimate version?

If so, then is it still worth it to do resolve stacking with arbiter of justice?