I've played quite a bit of Jack/Flame and aside from some bad drops due to my own rustiness I haven't noticed any difference in the spreading. Flames have always been volatile, so to speak, in the regard of spreading, but generally speaking, the more you hit, the more they spread, and this makes it really important to hit as many as you can early, even at the risk of breaking streak, because it seems to have a cumulative effect on how frequently they spread later in the song.
It's also critical to stay vigilant and make sure you spot and hit the first flame note in a chain, because if you miss that, it could be quite a while until another spawns. It's just the nature of the beast; on busier songs with 5 lanes, and depending on how the highway is curving at a particular point, you could miss a starting flame that you never even saw and it seems like they never spawn.
That issue with the next flame note spawning WAY later in the song by putting it in a sparsely populated lane is unfortunate, but I don't think it behaves any differently than it did before the initial nerf. That's just something you have to take into account when choosing powerups; songs that have long gaps between parts on particular instruments can really hurt you in flame spreading if you're unlucky. And it doesn't matter if you "drop them once" in that regard; you can hit multiple flame notes, all of the ones that are available even, but if the spread pattern hasn't gotten to the point where it spawns more than one per hit, it can still put the next one way down the track and there's nothing you can do about it.
Thanks for the reply. I've been replaying songs this morning and beating old high scores. It likely my imagination given that some of my scores looked like they were done without power ups when I finished with my latest runs.
I never thought a game would be able to inspire the formation of a real band or strengthen friendships. Thank you Harmonix, for making Rock Band.