Like so many things in the Tankadin world, which Aura and Blessing you should use are highly situational.
My main 2 Auras are Devotion Aura and Retribution Aura. In situation where I am going to get hit pretty hard, I use Devotion Aura. In situation where I'm not going to take a lot of damage or anytime I'm in AoE mode, it's Retribution Aura.
I also tend to switch Auras during a fight. Let's say I'm on a good run of bad luck and just had a series of Dodge, Parry, Miss, Miss, Dodge. My healers are probably wondering what is going on as my life bar isn't moving, but my Mana bar is. I see that I'm low on mana, but high on health, I'll switch to Retribution Aura for 1 hit and go back to Devo. Changing Auras only costs you Global Cooldown, there is no Mana involved.
I don't ever use Concentration Aura while tanking. Everything I cast as a Tank is an instant.
The Resist Auras, I try to get up any time I know that I'm going to take damage from that element. You need to be smart about what Auras stack and which ones don't.
Shadow Resist does not stack with the Priest's Prayer of Shadow Protection. If you've got the Priest buff, don't bother with your Aura.
Paladin Aura's do not stack with Shaman Resist Totems. Keep that in mind if you run with a Shaman.
The question of Blessings is going to depend on how many Paladins you have in your group. My first choice in Blessing is again situational based on how hard I'm going to get hit.
For heavy hitters, my favored Blessing is Kings. If we have more Paladins my order of preference would be Light, Wisdom, Sanctuary, and Might.
In situations where my damage intake is less, I want Wisdom above all else. These are typically smaller groups, but after Wisdom, I want Kings. If there are enough Paladins that I can get Light in these situations, that's cool.
Keep in mind, this is just 1 Dwarfs opinion.