I don't know, this might be revisionist history on my part, but I would have been really interested to see the direction they took Worf in had Yar stuck around. I personally think it would have been better. Before he was Chief of Security, Worf seemingly was a "Bridge Officer" and a command track one at that. I saw him as someone who wanted to one day command his own ship, so he did this job learning all about starship operations to do it. He could do weapons, science, conn, ops, engineering... everything a captain needs to be able to do. This could have created great potential for story plots, especially since it wasn't traditionally Klingon like Security was.
Either way, did Chief of Security really help him much? I mean, what did that inherently change about his character. It allowed him to say things like direct hit, shields up, hailing frequencies open, shields down to --%, phasers locked, and other such gems. No, his development was tied to his character and his personality, which is how a lot of characters were shaped. Jobs had little to do with it. When the characters become just reflections of what they're doing, that's when the show has failed (IMO, of course). Worf was a character with lots of potential with or without his job and he probably would have had a lot of interesting stories with Yar there or without her there.
