Is not dps'ing that rare?

[Sylvain]

It is not rare

But no matter what other people say about DPS.

Your first, main and only concern should be : healing

If you know the fight, know the downtime, know you have nothing to do for the next few seconds, and feel comfortable about it regarding the state of your mana, you can and arguably should throw some dots.

If you are not comfortable with stopping healing because you don't know the fight, aren't sure about downtime or just don't feel like you can afford loosing 1-2 global cooldown on the boss. Do NOT do it.
If someone dies because you were dpsing (I mean, they died from a lack of healing, not from standing in a instant death aoe marker), you'll never be able to do enough dps to overcome the dps lost by this death, even if he you rez him assap.

So, if you are "noob" as you pointed. Do not do it.
If someone complain "healer can you dps", reply that you don't feel like you know the fight enough to do so.
In any case, it has been confirmed that fight are balanced around healers doing 0 damage. Which means that if your group cannot pass dps check, it is not your fault. It's the dps not dpsing enough.

If your group keep failing a dps check by a few % (like, 1-2), your dots and dps can definitely help. If they fail by 10-15%, unless you simply stop healing there's no way your few dots and broils will help.

Your job, above all, is to heal and do mechanics.