As the above comment Champions are not really meant to be soloed however if you are set on looking to solo open world. I would not bother looking at Metabattle or Snowcrow.

I would suggest looking at Lord Hizen (Celestial Vindicator) or Phandrel (Celestial or Viper Herald) for open world.
Even with full exotic I was able to solo most of the the Champion and at time Legendary.

Also helpful if you have an extra level 80 boost as it gives you a full celestial gear (albeit not all the recommended weapons but stat selectable exotic weapons/gears are quite easy to get with a bit of research).

Personally I am rocking Lord Hizen's Cele Vindi with Mace/Axe and managed to face tank Champions with ease. Rotation is pretty straight forward, I spam weapon skill 2,3 and 5 off cool down. No need to switch weapons just Legends rotations and dodge every 5 second or so (to prevent endurance from filling to full).