You don't get to pick though. That is a huge downside. It makes it tough to build and execute a plan. It might be worth picking up, but not over something more reliably good.
It doesn't make it tough to build and execute a plan. This is how you do it:
1. identify a key $5 you have to buy on turn 3 or 4
2. buy Bard
3. Bard lets you buy that key $5 on turn 3 or 4
4. Have Bard collide with your terminal 5 cost card you just bought in the next shuffle
I mean, sure, Bard can be good at getting 5 in turns 3/4, so it sometimes can be a good opening, a bit like Horse Traders (though HT is definitely better at reaching 5), which is a decent opener, but Horse Traders gives +buy which can be super important later. One thing to also note is that Silver is also actually a pretty good card at getting 5 and you will always have that.
But, yeah, if you have spare actions and/or want action payload Bard can be a good card, but that's pretty much the same situation where you would get Fortune Teller, Navigator, Harvest and a few other power cards... (granted Bard is probably better than those, or at least in the same level as Navigator)
It's way better than Navigator. It's more comparable to Scavenger's power level.
Eh.....not sure I agree. Scavenger's midgame of trashing mostly Copper isn't great, but its late game of trashing Province to help buy more Provinces is pretty good.
You have argued that Bard is not weak because it's good at hitting $5 and giving money early. Sure, I agree. But Silver isn't that much worse than Bard at helping you hit $5, and it's non-terminal. (I'd like to see the math if you disagree.) Is opening Bard worth not opening the other $4s, and worth having an extra terminal in your deck? I would guess that the answer is "No" at least half the time. Is buying Bard after the opening worth it? Again, I'd guess "No" at least half the time - there should be terminals you want instead by that point. At which point I'm more inclined to place it closer to Navigator in power.
I'm pretty sure Bard is stronger than Navigator. Many of the boons can be good throughout the game, and I'd be much more inclined to play a couple of Bards as payload each turn than Navigator. Some boons even help you cycle in the early game, like the Dungeon one.
Similar to tracker and Bard, there is also Sacred Grove. I see why that card was made to give symmetrical. Is is very potent with that +buy.
And yeah, you are thinking of Salvager, but #3 in Awaclus's list is the Salvager comparison (with Flame's Gift).
To give some more credit to Awaclus's argument, Nocturne introduced a bunch of Night cards that cost $5 (and Raider at $6).
Maybe the appropriate comparison to make for Bard is Monument. Are the boons that Bard gives going to overcome the +VP from Monument? Maybe, maybe not. Certainly in any game with a throne variant, you'll want Monument.