Phoenix Adept - I'm still learning and using this class as I go, but this setup was one that worked out pretty well for me, and that I will continue to use.
http://narida.pytalhost.com/me3/classes/#04LLRIDM9@0Weapons: Carnifex or Phalynx
Singularity 4: Increase duration 30% and additonal targets can be floated
Singularity 5: Lifted targets take damage
Singularity 6: Detonate singularity to do 500 damage across 7 meters
Smash 4: Increase damage and force 30%, add biotic effect that can be detonated
Smash 5: Increase damage and force 40%
Smash 6: Increase radius 50%, and add 1 additional target
Lash 4: Increase force and damage of detonations by 50%
Lash 5: Do 100% additonal damage over 10 seconds
Lash 6: Penetrate shields and barrier and lift any target without armor for reduced damage
Phoenix 4: Increase damage 10%, increase weight capacity 20%
Phoenix 5: Increase power damage 10%
Summary - I'm still working on the details of the class, but this seems like my best option. Like all the characters in the Rebellion pack, the fact that races have 2 shared powers forces me to attempt to rank them up differently so they don't feel too similar. For this class, I choose to rank up biotics.
Increasing singularity will help biotic explosions since Lash and Smash can both set it off. Lash is designed to increase detonation power and get enemies from out behind cover. It's already a spammable power, so no need to worry too much about increase speeds.
Smash has a number of ways to rank up, but I choose to go with biotics in Evo 4 to setoff Singularity or Lash. Since the power takes so long to actually occur, I forgo speed options for power. I also choose to hit multiple targets with this power since it will be your only crowd control move.
Another thing to note is the power wind up times. Smash and Lash take quite a while to actually be performed, so making sure you have cover is almost necessity with these 2 powers because you expose yourself for precious time that could mean a death.