Though Harrison kept up his solid dual tackle/sack pace in both 07 and 08, this is generally what you'll get when you hitch your wagon to a rush OLB. Ware and Harrison contribute enough (usually) outside of the pass rush columns to have okay value on their non-sack weeks, but most other rush OLBs will not. Unless you're willing to take the bad with the good (and hope that the good happens more often than the bad), there are two situations where these guys make sense in your lineup.
1. Big play scoring system.
2. LB2/3 alongside a number of other consistent lineup performers where they're bad weeks won't hurt you much.