The real question here is "What is your definition of "serviceable" DPS? And how is this the same/different from any other class or archetype? I think I do pretty serviceable DPS as an Enchanter. But that is probably because I solo and have no real comparisons to other classes/archetypes. What I have noticed is that my DPS gets better and better depending on a number of things: ALWAYS be leveling up your skills. As an Enchanter I swap my weapons frequently to make sure that my staves and daggers are maxed. You never know when you're going to get a special version of what you like or don't like. It is better to have your skill maxed than to wait for an item and then having to spend a long time leveling up because we ignored it. Next, always go for that weapon upgrade. It DOES matter from one level to another. FOOD is another factor. As an enchanter I don't have much use for something that gives me +2 AGI. At least not when I can carry food that gives me +1 Int (+damage and + mana amount), food that gives +1 Wis (also enhances my spells but also gives a higher rate of gaining skill ups), or even food that gives +10 run speed. Your food matters. Never be afraid to ask in chat for food for your class. Tanks would love to have food that gives +100 block and +5 parry. Another thing to consider is your own abilities - learn them use them and most importantly, when given the option - throw some Master points into them. Lastly, consider your role in the current encounter. Are you a DPS machine or is your job to take a pounding while others DPS? Having a second tank can be fine if you are expecting adds. Your DPS may not be as high as a rogue or a wizard, but if you have to hold a mob for a few seconds, your "serviceable" DPS is more along the lines of taking the heat until help can be had. Even if your DPS is lower than the rogues, it is still "serviceable" as an off-tank.
On my paladin my DPS was pretty low until I got a nice 2 hander with about 13-15 damage. Then, your damage will ramp up again when you get the Oath of Might ability which practically doubles your dps at low levels.