Basically my goal is to leap to a mop, ground stomp pull them together, cast a rend, and then spam the crap out of Seismic Slam and if I need to dish out more dps I pop down a frozen earthquake. Not the best for single targets but I'm still learning.
Unfortunately you can't really "spam" any of your abilities because fury generation is fucked, but, also as Wallach points out barbarian itemization is fuckeddddd.
I hate to burst the dreams of anyone enjoying the class, but, for some reason Blizzard didn't bother giving barbarian any items that make our spenders better (which is the only way to reach Torment 6 because of mob HP values) outside of a single 2h mighty weapon which unfortunately has the problem of being a 2 handed weapon. It will actually be great in 2.1, good enough for Torment 6, but, not high end GRs.
I guess it's worth mentioning 2.1 will add 2 items that buff our spenders, but, both have already been confirmed as terrible. Of course that doesn't mean they won't always be terrible, blizzard has buffed quite a few legendary items to make them go from straight shit to god-tier (such as tall man's finger and firebird in 2.1) but for now they aren't great.
The only endgame paths for barbarians are based around our 3 class sets which are all pretty decent (and in 2.1 all 3 will be amazing). While it does suck I will say at least those options are fun to play. Both Raekor and Leapquake are styles I enjoy playing (or else I would have ditched my barbarian a long time ago)
Bro every Barb is going to use that 2H that increases Frenzy stacks to 10 then use Golgok, Simplicity Strength, Pain Enhancer combined with Depth Diggers and a bunch of procs plus Battle Rage Blood Shed and Overpower Killing Spree for insane attack speed DPS!!!!!
I actually wouldn't be that surprised if that was somehow T6 capable. Probably sucks for AOE, but that would be some pretty good single target damage. Either way though, still doesn't address the issue of all our damn spenders being useless.