"In one of my leagues, there is a huge emphasis on DEF. There were multiple weeks that a DEF was the highest scoring player of the whole week. So what I'm asking is, based on that info, what round would you grab a DEF?"
So in discussing it further with Johnny, I learned that he was in a 12 team league, and the drafts has 18 rounds (meaning he'll likely be taking 2 defenses in the draft). And so here is my reply, and although I didn't give him a concrete answer, I gave him a lot of things to keep in mind when deciding WHEN to draft a Defense.
"Allow me to throw a lot at you.... consider this... In one of my  leagues, yeah, there were 6 defenses in the top 25 fantasy players overall. So defenses are big point scorers in my [many] leagues. But no matter when you take a defense, the success of that pick is all in whether or not you HIT or MISS on the pick! In 2012, let's say you were using espn's cheat sheet for taking a defense. They ranked the 49ers 1st, the Texans 2nd, the Bears 3rd, the Seahawks 6th. If you took one of those D's, bam, you HIT, because they all finished as top 6 defenses.
Flip side of that coin, ESPN had the Ravens 4th, Eagles 5th, Jets 8th, and if you went with one of these defenses, you MISSED, because they finished outside of the top 15 defenses.
In the 2012 ESPN draft guide I'm looking at, Broncos were ranked 23rd heading into the season, yet the Broncos D finished as a top 3 defense. Bengals were ranked 17th, they finished as a top 6 defense in 2012. Rams were ranked 18th, and they were top 10 defense in 2012.
The point being, even if you jump on a defense early, hard to say if you're going to HIT or MISS. And if last year was any indication, as I mentioned with Broncos/Bengals/Rams, you can still get a top 10 fantasy defense on the waiver wire, during the season, if you catch on early enough before somebody else scoops them up.
I don't know that I can take a defense before I already have my QB1, RB1 and RB2, WR1 and WR2, RB3/WR3(whoever my starting flex is), and probably even my TE1. So if you do the math on that, around round 8, you can consider going defense, if you really must. Or, you may feel forced to do it sooner if a "run on defenses" starts in earlier rounds. Let's say it's round 6, and somebody takes the Seattle D. The next person may be compelled then to take 49ers D. If you are the next pick, maybe you say "damn, I'd better take a D now", and you take Broncos or Bears D, bc you are sure they're gonna be top performing D's in 2013. But what if that "run" happens right after you just picked(let's say it's round 7 and you just took a TE1)! By the time if gets back around to you in round 8, you're probably going to have 6-8 defenses off the board, maybe more, and at that point, I would probably then wait until the later rounds unless there's a defense I know for sure is worth taking right there.
I am one of those guys who doesn't tend to spend a high pick on defenses, because a lot of times I'll just add/drop D's based on matchup week-in and week-out. So I will draft a lower-tier D1 defense as my "starter", let's say I get Rams/Giants/Packers D, I don't have to get them early, bc they are ranked in that 9-12 range, ie, ranked as low-end D1's. But I may then draft Bucs D in the later rounds as my D2 (NFL.com has them ranked as the 18th fantasy defense), with the intention of starting them in week 1, specifically bc they face the Jets, and I think the jets offense is going to get eaten alive. But then I'm ready to drop Bucs D in week 2, bc they face the saints (and bc they also face patriots in week 3). I only wanted them for 1 week. Then I either start my regular D1 in week 2 (if I like the matchup), or, I look over the waiver wire to see if I find another available D that has a tasty matchup in week 2.
More so than with ANY OTHER POSITION, you can play the "matchup game" with defenses.
Here's something to do, go look at the 2 guys who made the championship game in your league last year. Did both of those teams have a top 5 defense? For example, if the league champ had Packers D, the runner-up had Vikings D, then that tells me you shouldn't worry much about getting a top defense. On the other hand, if league champ had 49ers D, and runner up had Seahawks D, well, then maybe you should try and get one of the top ranked D's."
Johnny then replied that he checked out the 2 teams that made the fantasy championships in that league last year.... He informed me that both were 7-6 fantasy teams (ie, not exactly dominant!), and that one team had the Seahawks D, and the other team had the Patriots D. And if we go back to a site like an ESPN.com and see the 2012 rankings, Seahawks D was ranked 6th, but the Patriots were ranked 20th. So what's that say to you? Well, to me, that says it doesn't really matter that you draft one of the top 10 ranked defenses, but it is important that the defense that you DO draft finishes in the top 10-12 of fantasy defenses. And as I mentioned, it's not always a guarantee the the defense you draft high, will finish as a top fantasy defense.
Having said all of that, the only defenses that I'd feel comfortable jumping on somewhere in that round 7-9 range, is the Seahawks, 49ers, Broncos, and Bears. And you know what? There's a solid chance that one of those teams won't finish as a top 10-12 fantasy defense. And for that reason, I probably won't be taking a defense until the later rounds, just like I do every year...
Good luck, fellow fantasy addicts!