I have fun with my Sonic/Dark. She's not soft-capped (although she does lean on Ritual of Protection), but Sonic and Dark both include stuns and sleeps to take mobs off the board, temporarily.
Typical attack chain is Aim > Dark Pit (stun) + TP into middle of crowd > Soul Drain (dmg boost) > Dreadful Wail (another stun stack, to stymie bosses) > Kill kill kill everything that's still standing. The Soul Drain lasts 30 seconds, and when it's running full power Death Shroud helps the mop up really well. If other enemies are attacking from range, there's Siren's Song to put them out.
I took the Soul Mastery power pool for Oppressive Gloom, I use that and Screech when I'm dealing with a boss,
I'm still learning how to use it (still taking plenty of dirt naps) but it's a lot of fun, and a pretty cheap build, all things considered.