Cates isn't that bad offensively, if you played him with Farabee and Brink, I suspect he'd give you top 3C production (which actually isn't that much, the median 3rd line forward (#240) produced 23 ES points, the median 2nd line (#144) 33 ES points).
Cates had 28 ES points as a rookie, 14 in his last 38 games last season (when he was healthy) which is similar production.
Farabee/Brink would be perfect for him, Brink is a playmaker, Farabee a shooter, and Cates can CYA for them. It would likely be an above average 3rd line.
Which is why keeping Luchanko up is puzzling, Torts must really love him b/c I don't see where he'd be this great improvement over Cates unless he's better than we think.