Yeah, I don't have the time to watch every single snap of Walden's 2016 season with the Colts.
Neither did I, but we have a good idea what the Packers do.
One key aspect of playing defense, which applies especially to OLBs, is changing gears from pass call to run play or visa versa since the opposition does not give you the play in advance. Capers asks his OLBs to take an outside rush for edge run defense and pocket contain to minimize mistakes in pass/run or run/pass transition. Pass rush pressure is supposed to come from second effort motors. You just don't see much in the way of stunts, inside swims, jet rushes or free lancing.
Other DCs take a different, less risk averse approach. If the Colts used Walden regularly in jet rushes, which would account for the sack count, then the run grade is going to suffer. I cannot say if they did or they didn't.
You would expect Packer OLBs to grade higher in run defense than their abilities might reflect assuming they follow the prime directive. And even under that prime directive, these guy's run defense was not very good. Elliott looked to improve in this regard, but the pass rush suffered...the package simply isn't there which explains why he wasn't tendered.
Fackrell may turn into an NFL football player; or he may add bulk and lose quickness. Elliott is a core special teams player and that's about it. I don't think you want either of these guys playing 2, 4, 6 games as an injury replacement.
Walden would be a known, veteran quantity. He's not going to excite anybody, but you'd expect him to be assignment sure in an injury replacement scenario. And he wouldn't cost very much.