Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
If it is a very long match, Singed is also very good with some ap. When that happens, i switch Thornmail out with Archangel's staff, and Rod of ages out with some more ap [abyssal Sc epter] or with Frozen mallet, so he gets some more health, dammage and slow the enemy while he attacks. Or what you prefer.