One thing is for certain; the current system for IDP is flawed and out of tune with the value and importance of pass-rushing linebackers in the NFL. Teams don't play traditional 4-3 or 3-4 any longer, they're all hybrid defenses where players move around so it's totally arbitrary when the value of players go up and down so drastically because of coaching/formation changes when they basically keep playing the same position in real life. It's just a base formation change, it's not like their assignments are drastically changed. A pass-rusher is still going to rush the passer, regardless of what his position is on a piece of paper.
To me the solution to this problem is obvious. FF sites like MFL needs to start giving more accurate descriptions of LBs; e.g. ILB, 4-3 OLB and 3-4 OLB. That way leagues could decide for themselves if they want to group 3-4 OLBs together with the other LBs or with DE or DL. Basically all the 3-4 OLBs primarily pass rush with the exception of Courtney Upshaw so it's not like it's super complicated with tons of 3-4 outside linebackers that doesn't fit the mold.
Or even better...I'd prefer if all pass-rushing LBs were designated as ELB (EDGE LB). That way pass-rushing 4-3 SLBs like Von Miller could also be grouped in with the other pass-rushers, or have position specific scoring for ELBs that balances their scoring versus DEs. And this would still give conservative leagues the ability to keep grouping all LBs together if that's what they want to keep doing.
The system is screwed up and needs to be changed, it's just that we're so used to this way of handling it that we don't see how dumb it is when we're chasing inside linebackers who stumble into volume instead of rewarding the elite pass-rushers. Good pass-rushers are known to play the second most important position after QB in real life football, but in IDP most of the top pass-rushers perform like LB3s.
Yes, you can tune things with big play heavy scoring, but that still doesn't solve the problem unless you go insanely sack heavy and at that point you'll start seeing some wild game to game fluctuations. Besides, Clay Matthews and these guys would have much more positional value if grouped together with DEs since the LB position doesn't drop off the same way it does at DE. And DEs already have inconsistent scoring which would match up well with the inconsistent scoring you'll see from 3-4 OLBs.