So I managed to get close to level 40 before end of beta, and these are my final thoughts on the changes at this current point plus some stuff I wouldn't mind seeing in the future.
I spent the last few levels about half solo and half in a party, and the rework felt fine in both situations. In parties I would say I pulled a bit more than half of the time, just depended on what we had in the group and what we were fighting.
Solo was pretty simple, just run around and kite with the DoTs. This was a little slower, albeit faster than it was before the rework. I was mostly just using movement speed and both DoT songs, sometimes having to do hp regen if I got smacked by the mobs. I would usually have the damage shout on my bar for this but rarely used it since the range is just too short and risky. I would've liked having a 4th song that helps with solo, and I had considered the new AC/bubble song but with it being Wind it just didn't fit with solo where it's a little more stressful to be swapping instruments.
In parties I still kept a pretty standard core of songs, and in all cases I was the only source of haste and mana regen so that took up 3/4 of my main songs with the 4th being just hp regen until I needed to pull. Sometimes I would cycle in either an aoe slow or the DoTs if I wasn't needing to mez, and otherwise would pile in and melee with all the extra STR from whistling slash. I honestly didn't really pay attention to whether I had any significant falloff of song buffs, and I imagine that's something that'll get smoothed out with later updates.
Most of my feedback is in regard to group content, where I think bard is still a bit lacking. First off, there's still not really a lot of variety in group songs.
The new AC/bubble song is probably fine at higher levels but it starts off with much too low values that it's not worth using until basically max level, and even then I'm not sure. If it doesn't get a bonus to the bubble from CHA then it possibly should to be a consideration.
I think the combo hp/mana regen song also comes a bit too late in levels and might be better received in the late 30s or early 40s. Likewise, I still think bard should get more combined songs. Maybe combine the spell haste and secondary haste songs somewhere in the late 20s, and give an upgrade to it at higher level. Same thing with the Beats of Battle/War line, maybe let Battle scale to 42 and then combine War with the primary haste at that point.
It's not really clear at this point how useful the resistance songs will be, but I had no reason to use them. If they maybe had a small AC component or something, and maybe an upgrade with a damage shield or something would give more incentive to use them.
I would really love to see more songs that made use of the instrument modifier, because right now Crescendo feels fairly lackluster in group play. If there's a component to mez/charm/lull to ignore a certain amount of the target's magic resistance, perhaps the instrument mod could further that effect and would incentivize using instruments for them. If I've missed something and that's already the case it would be nice to see in the tooltips what values are modified or not. Currently it feels like you really just equip a lute full-time in party for the mana regen and that's it, sometimes swapping to a drum. If each instrument had a clear "role" that could go a long way with reducing instrument swapping during a party but still making each type relevant. Or possibly having certain songs get modified by multiple instrument types would open up better variety in instrument use.
With that all said, I'm enjoying the rework quite a bit and I understand things are still going to change through EA and beyond. I'm excited to see how things evolve over the coming months/years for the class and I'll continue to provide (hopefully useful) feedback!
TL;DR would love to see more combined songs to give more variety in song selection, and more songs modified by instruments with possibility of songs being modified by multiple instrument types