In addition to killing Kargath Bladefist on Heroic difficulty the first week that Highmaul opened, over the past two weeks we have made runs at various other bosses on Normal difficulty. We were able to kill the Butcher, and got some practice in on Tectus, Brakenspore, and Twin Ogron on Normal difficulty.
Apparently that practice along with a little more gear paid off: this week we were able to defeat the Twin Ogron encounter on Heroic difficulty. (And to top things off, we went in and one-shot Brackenspore on Normal). Great fun was had by all! :)