You might want to have a look at the talent tree and see what the talents are to determine whether they are useful for you or not:
Keep in mind that Defensive Stance increases threat generated and decreases damage taken, regardless of talent point allocation.
While leveling, even if mostly tanking dungeons, warriors will put points into the Arms tree, and swap between a two-hander and 1hander/shield while tanking. This is typically because the added armor or block from shields is sometimes useful, as is being able to shield bash early on, but the added damage of a two-hander is often more helpful for threat.
Damage mitigation isn’t often the primary concern, but whenever a shield is of use, you can simply hit your weapon swap macro keybind and swap, because you can switch weapons in combat.
Stance dancing isn’t uncommon, especially while leveling (Charge, for example is usable in Battle Stance, so it’s common to open in Battle Stance with charge), and the arms tree gives you access to Tactical Mastery which helps preserve some rage while switching stances, and later on opens up Sweeping Strikes, which is great threat with a 2 hander.
I’d have a look at Elite’s Warrior tanking guide, which is aimed at newer warrior tanks for WoW Classic. Maybe you’ll find some decent pointers.