I summoned a giant in a desert and gave him a name so he wouldn't despawn. Later after being unable to find him I can only assume he got killed by the abundant cacti, which is really sad.

I know this isn't a bug per se and the Giant isn't exactly an in-game mob, but as you did just update the armor to show correctly, I hope you will consider making Giants immune to tiny damage like cacti. They shouldn't get killed by it any more than I get killed by fiberglass insulation (though I could see an argument for them stepping on cactus and running the other way).

P.S. Giants riding other animals looks hilarious. Especially bats.