One of the versions of Zombie's giantslayer deck (cremation/lava golem) had a single heavy armour just to help against things like fire shield, but it wasn't an integral part of the deck.
The only time I've ever seen heavy armour used in a practical way was in combination with Otyughs, so that they can devour more things, obviously. You could also use it in a deck with gravity shield on your opponent's creatures to prevent them from attacking; this could possibly work in an earth/gravity duo that had otyughs already anyway, although anything that gets through gravity shield can just be eaten by otyugh. It could be used against venomous creatures that would poison the otyugh.
That's about all I've got for practical uses. It's a very rarely used card, and I don't think I have ever used it myself, either unupped or upped.