It's really not that hard to do. Basically, instead of standing in the back going through your line of spell macros, you can be up front engaged with the mob, and going through the same line of spell macros. RDM can deal damage, but not nearly enough to draw any attention away from the tank or other DD's. Just watch out for AoE's and keep an eye on your dialogue box for when buffs/debuffs wear off. Again, nowadays it's a moot point since people don't want anyone feeding TP to the mob.
I think a lot of us sort of lost sight for a long time in this thread. It's not about keeping up with dedicated, specialized DD's; it ain't gonna happen. The damage a RDM deals is secondary, like one long DoT. If RDM were able to even partially hold a candle to normal DD's damage-wise, the job would be beyond broken. RDM fills a jack-of-all-trades role, and can make everyone in the party's lives easier if played well. Nowadays nobody wants a hybrid though, everyone wants all specialists all the time.