the value of hit / expertise
a question very often asked is, whether we need to be hit or expertise capped. The answer is: It depends on your dps. Hit and expertise scale directly with your dps. The better your gear gets, the higher the value of hit/expertise gets. When in blue gear, both contribute very little to your dps. With ulduar bis, they are quite important, but still not the best stats. The same holds true for t9, although both are more important when you have really good t9 lvl gear. When you have a lot of ilvl 264 gear or higher from icc, they turn out to be extremely good. Try to reach the caps then. Only arp will be better (and only if you're near the hard cap). Also, there is no such 'magic threshold'. Both stats always have the same value (as long as below the hard cap), no matter if you have 0% hit, 3% hit or 5% hit. That means the two stats scale linear.
But - for a beginner it could be quite confusing missing a lot. Our dps priority is already hard enough even without our attacks being dodged. It could mess up the dps of a beginner, if his hit and/or expertise is too low. If you consider yourself weak at maintain a stable cycle, then more hit/expertise could help to stabilize it.