Rogue Dedication seems most useful to me, given that Heavy Armour only really improves AC by 1 at the cost of your movement speed, and it'd cost you a class feat to make it relevant later down the line.
By comparison, a Maestro Bard can potentially extend their Dirge of Doom through Lingering Performance, thus avoiding paying the action economy cost. You can also get some action enhancers through Rogue, such as (the somewhat unreliable) Nimble Dodge (you'd need Basic Trickery to qualify for Dread Striker anyway), Skirmish Strike at level 12, as well as the potential for Master Reflex saves at level 12 too, thus helping with your squishiness.
Adding to all this, you have access to Heroism, which can provide a long lasting boost in important battles, meaning that you would comparatively end up hitting someone at -3 AC (-1 Status, -2 Flat-footed) with anywhere from a +1 to +3 Status bonus to attack and damage.
Given that critical hits are more likely, it is a pity that most Bard weapons offer a redundant critical specialization. I'd probably use a Rapier most of the time due to Deadly, but using a Light Mace might also be fun for the forced movement.