I understand the rationale for picking him off waivers.
He's an experienced player who fits the role of a penalty killer and plays a simple physical game. None of the players in camp (including Gabriel, Bussieres, Bulmer, etc) are talented enough to overlook their inexperience and frankly none of them have been impressive in the minors. Losing both Cooke and Brodziak, along with Haula's unimpressive training camp, probably gave Yeo (who really likes grinder types) a lot of hesitation.
I don't really think it's the best way to build a fourth line though. I would rather have a line that tries to drive puck possession, even if they are smaller or younger (Schroeder, Fontaine, Keranen, etc). Long term, I think they would have a net positive impact on your scoring and winning. It just seems that unless you have "elite" grinder types (Cooke, Clutterbuck, etc) you are writing off production from that fourth line.
Hell, look at last year. The fourth line scored a ton of goals because of Zucker. I'm not saying you should drop Zucker to the fourth line, but that placing a fast, skilled player there can create a mismatch that exploits weaker competition.