I'm working on my tac officer now. He's up to RA Upper Half. Had planned on getting the Defiant Refit but you're ranking it last... Okay maybe it is last, but at least it looks cool.
I like the Akira also and was disappointed that it was only a tier 2 escort.
Well, it does have its perks: 5% more Shields than the FE/AE (but the AE can fit a 3rd Field Gen), better Turn Rate and the Cloak.
The Cloak is great in PvP, but in STFs you pretty much only use it once, afterwards you're pretty much always engaged, and the difference between 15 at 17 base Turn Rate isn't that significant.
In STFs, even my Luna (13 base Turn) has no manoeuverability issues and in PvP 17 won't suffice to keep up with BoPs (and it shouldn't).
The downside is the 3rd Ensign Tac slot.
Overall, it's not that bad and you'll find plenty who disagree with my ranking above.
BoP: are you sure it's not just a Torpedo Spread of Quantums? They might look smaller because of the angle or something.
Personally, I favor Antiproton weaponry on Escorts/Cruisers/BoPs, Tetryon on the Luna but I'm not sure they're "the best" overall.
The Phaser proc is very strong, so's the Disruptor proc (but I'm not sure if it stacks from different sources - that's the main reason I switched to AP), Tetryon can be as well if you've specced Flow Capacitors, Polarons have the 2-pieces Jem'Hadar set bonus.
Plasma's the only bad type, the rest is fairly comparable.