[Kameron8]

The other dispels are very rarely used- requinite is saved because its class-flexible and you simply lose some matchups without the ability to null off statuses.  Pressure Fletch costs Annorum, a much bigger resource than an Arcane Gun overcharge, washes away three status effects, and has no method of being passively built up like with Spark Drive or Thunder Drive.  Wash away is bad too.  

That's the reason Magic Gunner is even seen nowadays.  It's the only class with reliable dispels, an important mechanic in way too many matchups.

As someone who uses Spark Drive, Null Shell, and single shot weapons, I agree with the above sentiment.  Reliable mass dispelling is obviously very powerful, but it's one of the only means left of shutting down buff stacking that doesn't cost more resources than it's worth (Pressure Fletch) or rely far too much on lucky RNG (Wash Away, Requinite).  Null shell cannot purge statuses if the Magic Gunner can't make the required hit check, and can't access Spark Drive without critical strikes.  Outside of dispels and interference, or the occasional knockdown against poorly positioned teams, there isn't often a good reason to take single shot gunners into a party.

The primary things to be looked at, in my opinion, are the statuses that are dispelled, but really shouldn't be.  Knockdown immunity was already addressed, but things like Guard, Unmarkable, Silence immunity, Stun immunity, etc, go away when realistically they have no business doing so.