combined with unyeilding which gives a small amount of all round resistance (apart from psi), the two passives resit energies and elements give about 20% res when all are 3 slotted.
RPD is worth taking and 3 slotting purely because it is passive and adds to temp inv and unyeilding's resitances.
You get RPD by deafult so all have it.
But imo resist energy/elements aint worth taking, There are alot better powers to get. And i for one didnt notice a big diffrence between when i had em and now when i dont. Not compared to the diffrence i noticed when i got Tough from the Fighting tree + i got boxing also.
Depends what type of Brute you are. The passives don't give a big Res boost, but every little helps. Especially if you get toggle dropped, at least you have some fallback Res while you're getting the toggles back on (unlike Dark Armour for example).
Frankly, I think every power in the Invuln set is worth taking, but I'm from a Tanking background and would say that. 
Put it like this, there's no need to prioritise them. If you find you have free powers picks when getting towards the high levels, take them. If not, you've probably found other powers to be of more use, so don't worry.
Oh, and you'll want Energies, then Elements, then Tough Hide.
Thx All
You might want to check out the Tank/Scrapper defn's of Invulnerability as well; there's not that many changes between them.
Are the auto on powers in this set (Resist physical, elements, energies & tough hide) worth choosing. If so what defense boost do they give and are they worth slotting??
Thank in advance.