http://grimcalc.com/build/yurFdT
Thought I’d post my Spellbreaker, not so much as a guide as it is far from definitive and short - but just as a report of my first and only class. Got lvl 85, beat ultimate in a bit over a week, and did most of it without any help. Wasn’t very hard at all, even with trash gear. I’m not super special or anything, I just lucked into a really easy beginner build.
Items - Just look out for cooldown reduction, cold damage/frostburn, on-being-hit proccing item abilities, resists and general tankiness. CDR is king, every % helps immensely. As far as grim calc goes, I showed what I actually put points into as I had a lot of +skills. You want Mirror and Blade Barrier up to level 12. I never had more than 6k health.
Explanation - Essentially you just manage Mirror and BB cooldowns to stay near invincible in all fights. There will be a few second bursts of vulnerability in between abilities but I rarely found it a problem. Pop Flash Freeze when either ability ends and just shadow Strike/run away. A lot of builds on here seem to require good gear but I think this is probably one of the easiest builds to beat the game with, as you don’t really care how tanky you are so long as you don’t get one shot.
Rotation: Shadow Strike in -> Mirror -> Spam damaging abilities and auto attack with melee-> Wait a few seconds after Mirror expires if possible, pop Blade Barrier -> Wait a few seconds if possible, heal if required, Shadow Strike/Run away or just go back into another Mirror if enough time has passed.
There are probably lamer builds out there, but this one was pretty lame. I’d definitely recommend it as it is not at all gear dependent.