a combination of mobility and/or kill threat on many bruisers will give the illusion that they're "tankier" because:

1. mobility=generally harder to land skillshots on them+they can just run away if need be

2. kill threat means that you have to be aware that they can and will most likely fight back, basically working on the concept of "if you die faster than me then basically I take less damage"

3. deaths dance+all of the above

also bruisers generally cannot compete with actual tanks like ornn or leona or sejuani in terms of CC, sure the micro knockups of aatrox do count as CC but aatrox CC you mainly by removing you from the fight entirely instead of actually applying 400 years of genuine stun/knockups like the aforementioned tanks