What's wrong with trying to trade/move around so that the BPA is at your postion of need? Ideally...that's the answer.
I have no problem with going need over (perceived) value, as long as the player selected isn't an obviously inferior prospect. I'm not passing on an NFL draft 2nd round WR to take a 5th round RB even if I'm fat at WR and desperate at RB.
I don't think either extreme (always need or always "value") is the right answer. Every situation is unique, some needs are more desperate than others, some drafts are deeper than others at the need position, some prospects are elite and should always go first regardless of need, and some needs are so desperate only an elite prospect can sway me to go against my need (in SOME leagues...in others, trade partners are easier to find and needs are never so desperate!)
Call it 50-50 need-value.
There are actually 2 different kinds of value, not reaching and drafting underrated players. Trading/moving around can help you avoid reaching, so that you can draft need without sacrificing value, but if there are underrated players at a non-need position then you can't get around that need vs. value conflict.Not reaching for players means not drafting someone much earlier than where he is conventionally rated. You can solve that by moving around. If you have the 6th pick and really need a RB, and the top 3 RBs are off the board, then drafting Pead then would be a bad move. As long as you can get decent value in your trade, then it would be a good move to trade up to get Martin or Wilson, or to trade down to get Pead a few picks later + extra stuff.
The other kind of value is identifying which players other owners are underrating, and getting them for less than they should cost. If you think that Griffin should already be the #5 dynasty QB, then getting him with rookie pick 1.06 is an amazing value (even though that's about where he's typically going). If you trade away that pick then you probably won't be able to find a similar steal at another position, and even if you don't need a QB it could be worth it to try to trade for that pick to take advantage of that value.
4 different draft strategies you could take:
1. make trades to set yourself up to draft underrated players (close to where they are conventionally rated)
2. make trades to set yourself up to draft players at positions of need (close to where they are conventionally rated)
3. stay put and draft BPA
4. stay put and draft positions of need
These are ranked in order - ideally you'd mostly use strategy #1 - but you need to use at least a little bit of each of them (only trading if you can get a reasonable deal on the trade, and giving a slight bonus to positions of need so that you favor need when value is close).