There’s a reason they call them elites, they hit hard, and have high hit points and armor along with some nifty moves you won’t find elsewhere. Every instance is populated by elite creatures and more often than not, they are in groups. Having a firm understanding of how a rogue works in a group is important to be successful.
Elites that you find out in the wild (non-instance) are usually just named versions of some regular variety creature. They tend to be a bit more difficult than a normal version, harder to find yet are not close to the difficulty you’d find in an instance. The exception to this is the very high level elites

you find guarding certain areas (such as almost all dragonkin). They are meant to keep you away from certain unfinished zones.
As a rule of thumb, a rogue can solo an elite that is 2 levels under them. Of course, this can change depending on the type of creature you’re fighting. A giant for example will trample you easily but a caster will fall as quick prey. It’s usually best to attempt an elite with a friend as 2 people can easily take on a similar level elite creature. Always use evasion when tanking an elite.
Stun is usually a very good tool to use against elites since they have such very high armor that most of your skills do little damage. If you’re stunning them, then the rest of the group can get their damage skills to attack and they are not getting hit. This is a very good thing. Some people think Expose Armor would be useful here but it really isn’t. Creatures have such a high armor value that Expose Armor has very little effect and it prevents Warriors from using Sunder Armor, a tool they need to gain aggro. So stun attacks are key.
That being said, the bosses of most instances cannot be stunned. In those cases, it’s best to start with Garrote and throw on a Rupture as your other attacks will not do nearly as much damage. In later stages, bosses will survive 2 or more Rupture attacks due to their high hit point values.
To go over elites again: A rogue can solo them outside of instances with relative ease if they are 2 levels below them. In an instance, it’s best to stun elites due to their very high armor rates as special attacks will and can get highly resisted. If stun is not an option, then use DoT attacks. Finally, do not ever use Expose Armor – not only does it have very little effect but it prevents Warriors from doing their job properly.