The Palmaria actually has a very good aim time coming from the M109 and a respectably quick reload for a single shot arty. Its greatest advantage lies in its accuracy and excellent gun depression though, these two attributes make it very capable in direct-fire roles where it essentially becomes a big squishy TD.
That being said, single shot arties in their current forms are still flat out inferior to burst fire arties like the PLZ series. You live and die by your alpha damage, and being able to throw out multiple rounds quickly for that burst alpha makes them flat out better than single shot options in most circumstances. If you're just gunning for the Paladin, the PLZ-89 is a far more pleasant grind not to mention a better performer.
On the bright side, Palmaria is objectively better than the Paladin in every practical way. I'd say it's the second or third best single shot arty after the PLZ-05 with the single shot option, and the Cent 155 which has awful gun handling but marginally faster reload.