DarklordKyo said:
So I wouldn't be able to combo Banishing Smite and Swift Quiver, aww well.Also, since it's a concentration, I'd be able to use it on my bow and forget about it for the duration?
Yes, but all smite spells only apply damage once on your next hit. Once you've smote your load, the concentration is to keep the debuff up, but there's no more damage.
Also, would I need to use a component pouch to cast spells that require my lute while holding a Heavy Crossbow?, or could I reason my bard can hold the bow one-handed for the minute it takes to play the song? If neither, would I need Warcaster to use a Heavy Crossbow & cast magic?
You could totally grab your lute for a casting. (You don't actually need to play your lute, you just need to hold it) The rule for two-handers is that they need two hands to operate, not that they need two hands to hold. And as I said yesterday, a component pouch works fine. It's a bit less of an awkward image than juggling a lute and a crossbow too.
Either way, about the Swift Quiver recommendation from earlier, I figured I'd get Banishing Smite instead. Four d8s does less damage than ten d10s and two d8s, and they'd follow a Fireball. Besides, by then, hit chance could get to a point where you hit more often than not for most encounters (like how my monk is lvl 9, and has +10 to hit, though one of those points is from his Insignia of Claws, to be fair).
You seem to have misread Banishing Smite:
https://www.dnd-spells.com/spell/banishing-smite
"The next time you hit a creature with a weapon attack before this spell ends, your weapon crackles with force, and the attack deals an extra 5d10 force damage to the target."
The average result of a D10 is 5.5. So a Banishing Smite is only 5D10 (average 27.5) damage once. With 20 Dex a heavy crossbow shot does an average of 10.5 damage. In three shots Swift Quiver outperforms Banishing Smite for raw damage. The Banishment effect is prety great though.
Also, keep in mind what you'll be fighting if you pick fireball. If you're up against Devils it's completely useless.
Fire is one of the most resisted elements:
http://www.giantitp.com/forums/showthread.php?379165-MM-Resistances-Immunities-Vulnerabilities-and-Damage
If you're up against people or something Fireball is better than lightning bolt. If you're up against one of the countless things immune/resistant to fire, Lightning bolt will serve you better.