Comment below rating threshold, click here to show it.
Indomitable and Tough Skin were what allow auto-attack champs to trade with champs who use abilities to harass. This is especially true since auto-attackers are also usually melee, such as bruisers.
For example, Malph vs Vlad. Vlad can harass with Q, which has relatively low CD, and no mana cost, and suffer no minion aggro. Malph can't just trade with Q because his Q doesn't give him sustain, has longer CD, and also drain his mana. It's his combination of Q, and auto-attacks that allow him to trade.
Olaf vs Jax. Olaf doesn't suffer from minion aggro because he harass with the low mana Q, then E to the face. Jax need to trade with his quick AA+W combo. The latter draws minion aggro.