Hybrids and tweeners. Anybody else getting sick of that?
Situations in question:
3-4 OLB in Belichick's multiple front defenses:
Roosevelt Colvin, Mike Vrabel, Willie McGinest, Kamerion Wimbley, Bryan Thomas
These guys are LBs despite all this "hybrid" talk. They'll have no value unless you're in a league that greatly values sacks over tackles. Even then, their value may be questionable. Not all are proficient enough in any one skill (run support, pass rush, coverage) to be consistently valuable. McGinest and Vrabel have had good seasons as all around players, so too may Wimbley or Thomas in the future, but consistency will always be an issue.
3-4 OLB used primarily as rush LB:
DeMarcus Ware, Manny Lawson, Joey Porter
Similar to the first category, these three guys are LB by scheme, period. Because they are weak in run support and coverage or are rarely used in those roles, they are even more inconsistent than the first group. Lawson may eventually work himself out of this category. But these guys are probably spot starters in even the most sack heavy leagues.
3-4 OLB who are all around players:
Shawne Merriman, Steve Foley, Clark Haggans, Bobby Carpenter
These guys have proven to be talented across the board. Of course, some are less valuable than those in Category 1 because they don't make enough plays in the boxscore (eg. Foley, Haggans). Merriman is likely to transcend this pigeonhole in time after showing some ability in run support last season and an ungodly ability to make big plays in the backfield. Carpenter may prove to be valuable because he is a true all around backer.
4-3 defensive ends in "goofy" (read: confusing) defenses:
Jason Taylor, Terrell Suggs, Andre Carter
IMO, even though these guys do play a little coverage and are technically playing in a 3 man front at times, they are correctly labeled as DE. Obviously 4-3 ends like this are studs. I'd have trouble sanctioning a move to a LB designation as an MFL commish unless there is significant changes in how they are used on the field.
My approach is to try to understand the way these guys will be used within their schemes and then see how their skill set fits. It's always best to assume that they'll be "correctly" slotted before risking picks on them in a league hoping for a loophole of value. I don't disagree with Rovers that these guys are more valuable to their NFL defenses than to your fantasy squad. That's the case in many situations - Troy Aikman, shutdown corners, stud NT. Sometimes there isn't an easy scoring system fix. For now, unless you're seeing a transcendant player like Merriman, it's better to let somebody else frustrate themselves with these guys. It isn't worth the frequent 3 pt headache when you get a 2-1-0 boxscore half the time.