I think some around here still look at BPA as an absolute vs a tier thing. It's NOT take player 99 over player 100 regardless of need.....that's preposterous.
If you have a bunch of players all still in your top remaining tier, then of course go with need among the players grouped n that tier because you are splitting hairs anyway
Where teams blow it is when they reach for a player in an altogether lower tier to fill a need when they have a far better player still available left in a higher tier, but at a lesser need.
In that case, take the BPA (highest tier player) or trade down
I absolutely agree with the last bit: the most egregious violations of BPA are reaching to a lower tier for perceived need. Those picks almost always end up looking terrible.
But I disagree with "of course go with need." There are a lot more considerations than that, especially in later rounds when you're likely to have more guys grouped close together. Do you take a guy at a "need" position who can come in and give you some mediocre snaps right away, or do you take a guy at a position of less "need" who has all-world upside but is super-raw? It's not at all obvious and depends on a lot of factors. These days, when there are a lot of middle-class vets on the street who are going to end up settling for one-year prove-it contracts, I would personally tilt my preferences toward upside and away from need, but you really need a balanced portfolio of guys; you don't want to spend your entire draft on high-risk projects.
The other thing is that you're not always looking at a bunch of guys in a tier when your pick comes around. You may be looking at one guy, the last in a tier on your board, who fell to your pick for some reason, and then a bunch of guys who you have a tier or two below him. Think of Diggs in the 2nd, for example. You should take that guy, regardless of need, almost every time.
Finally, if you have "a bunch of players all still in your top remaining tier," your first thought should be to trade down if you can. Maybe you can't; that's cool. But you should try. Conversely, you may want to trade up for that guy I just talked about, the last guy in the higher tier.