I have been having some issues with my single target threat generation when I am main tanking. I have to ask some of my dps to slow down (druids and a mage, we are all roughly the same gear level). So I have turned to the TankSpot community for help.
My rotation is
IT,PS,Oblit, BS, BS, then just obliterates and blood strikes with icy touches and plague strikes to keep the debuffs up, Also Rune Striking whenever it is up.
I'd take a look at the Rune Strike Macro in the macros forum here. Manually clicking on the Rune Strike spell probably isn't letting you get the maximum benefit you can from the spell. It is very effective at producing threat when macroed. I would also add in Glyph of Rune Strike over Dark Command or IBF to supplement it's threat.
The next thing I'd try to do is put 4 points in Killing Machine. This can provide an extra critical hit every 15 seconds on average. The extra crits will go a long way to increasing your threat. I'd pull the points out of the Icy Talons tree. It's benefit is nice for the raid if you do not have an enhancement shaman, but if your dps has to slow down, you need the threat more.
Your expertise is 17 which is probably normal for your level. If you can increase it up to 26, it will help with threat.
The other best threat upgrade will be a weapon, but that doesn't usually come until the end of Naxx 10 which you may or may not be at. Get Death's Bite when it drops. The one you have is the best until you can get a 200+ dps 2 hander. If your server has Ulduar 10 Flame Leviathan only runs, get in on them and try to get Iron Soul.