LMs have improved sticky gourd which lays down a fire patch - I think damage and kills are credited to the player now, though.
You might try getting ahold of Evendale - he writes CombatAnalysis, so I suspect, of anyone, he's spent the most time trying to figure out how to parse combat log messages.
Oh, and yes, pet damage messages show up in the combat log, and I think pet kills show up in the combat log. There was an idea being tossed around a while ago to track flank attacks via the combat log. Nothing ever came of it, as far as I can remember, but the method for tracking it was via "<pet name> hits with Melee Flanked Min" in the combat log.
Not sure about soldiers though. I think they do.