So, I love playing a Shadow. It's good in PvP and uber in PvE.. as long as I use Tharan. As a DPS shadow I've tried using the other companions, and, I can handle 95% of things with any of them.
I can handle almost everything until I'm forced to fight an elite. Most of the time I can swing these as well with any of the other 4 by using all my cooldowns and a medpac. Sometimes that's not enough though so I bring the metrosexual techy along and down they go while I'm standing there trying to find any sign that I've been damaged at all.
I did have one fight on Belsavis that was sort of difficult because Tharan didn't realize that it might be a good idea to run away from the mobs PBAoE until I told him that Holiday was watching his stupid *** die. I did this by using Ctrl+2
So, I'd like to use the other companions. I use Nadia and Zenith when I want to get through some content fast. I use Qyzen or Iresso for... wait... oh right, I use them to do their relationship quests. I knew there was something. And I use Tharan for pretty much everything else.
Oh, and no other companion can mez a turret with a hologram!