Having taken Oath to 2 Waterbury tournaments and having played several local tournaments I started to ponder the usefullness of Arcane Laboratory in the sideboard. In all the games I've played I've never faced TPS, 2 Land Belcher, Meandeck Tendrills or some random storm combo deck. Now perhaps I'm fortunate but I think Oath has a favorable match up with these decks out of the box so why do you need Arcane Laboratory?
Don't count on that happening too much longer. I took Oath to SCG and played 4 (yes 4) belcher decks (2 gifts/belcher and a pair of 2 land) and 1 CA.
Maybe I'm making up for your lack of games against combo decks.