I probably could've worded it better. Allow me clarify a little bit.
Both of healers' nukes & DoT occupies a GCD, which means any missed nukes/DoT of GCD translates into potency loss. Now assuming we missed that one GCD for whatever reason (be it to heal, or we forgot to press button)...
- If we missed a Broil III...
RIP. That's a whole 290p of damage lost.
- If we missed a Biolysis...
RIP. That's one potential tick lost there, which is... 70p of damage.
In first case, you won't get back that 290p worth of GCD.
In the 2nd case, you may have missed a tick, but all that does is it pushes your Biolysis 1 GCD further back. At the most basic form, you only lose out 58.3p worth of GCD.
As it stands nowadays, our nukes makes up the majority of our DPS with our DoT (like you said) being the occasional 'cooldown'. DoTs are generally designed inefficient to be spammed but results in overall higher damage dealt per GCD if they fully ticked their whole duration. Individual ticks will always be weaker, that is true. But once active they will continue to tick until the duration is spent. Now what if a good portion of the healers' DPS comes from DoT ticks, a.k.a. each missed dps GCD only costs the healers a tick of their DoT instead of their beefy nuke?