The lastest games with Karn, vs Matt & Caitlin, went pretty well. It helped to have a slower start and thus get ignored for a few turns while I just built up mana, for the most part.
Lux Cannon was particularly helpful and it didn't hurt that Caitlin's demon deck removal had a weakness to artifact creatures.
A similar scene played out in the second matchup, with giant Eldrazi saving the day.
So I may be coming to the end run with Karn, having truly tuned it up for the better.
But...Kaladesh is out now and I picked up some cards at the release event. I think I'm going to remove a couple cards that aren't really doing much and add in a Bomat Bazaar Barge and Aradara Express. The Barge replaces itself and the Express could be a 5/5 with Menace using Karn.
I can't wait to check them out.