Just give it a few more levels... and in the mean time take on mobs that are a bit lower in level. By the time the mid 20s roll around rogues are very strong at grinding... and they only get better on the way to 70. Things like cheap shot (I think you get that at level 28) help a ton!
As others have already said, we weren't really built for taking on more than 1 mob at a time. As you get a bit higher you can take on more, and as you get more tools (like AR and BF, along with evasion, and vanish) you'll have plenty of ways of dealing with bad pulls or whatnot. However, a solid grinding/farming strat with a rogue always includes single targets. It's way more efficient to go from target to target. Even with all the above tools, you won't be great at running into 3-4 mobs and killing them. There is far more downtime (eating, lol rezzing, etc..) when you take on multiple mobs at once.
Just as a point of reference, a rogue wearing level 70 blue gear with a good epic sword/mace/fist weapon and a combat spec (or a rogue of similar gear with 2 good high output daggers and a 41/20 spec) can pretty much grind most high end mobs without eating (so long as they can pull them solo). I never eat or bandage when I'm farming. Occasionally if I ***** up a pull or get multiple adds I'll use WotF. I do generally slap at least 1 trinket on with a healing effect... and they tend to keep me topped off nicely.
Edited, Oct 9th 2007 5:52pm by LordMeridus