For the landscape of old-school Souleater DRK Zerging is the major one for the following reason: Double/Triple Attack (DA/TA) will override Occ. Attacks Twice (OAT), so DRK/NIN with a Kraken/Octave/MKris was always aware not to add either of the two to keep the number of OAT procs high.
So ignoring everything with respect to job, sub, damage types of the weapon, weapon skills etc. you can do pretty well with just Occ. Attacks X for raw damage if your %s are much higher than your DA otherwise would be.
That being said, DA/TA is usually better on the more intangible things. DA/TA procs on weaponskills, but OAT does not. OAT weapons are usually horrifyingly low damage. And if you are using Occ. Attacks 4x-8x weapons, you will turn whatever you're fighting into a TP spamming machine.
A relevant DRK discussion can be found here on the subject, although it doesn't address the zerging aspect of things. A quick Google around Blue Gartr and such should yield the old school discussions around this when Magians first started.