So basically, hulk has an 85% chance to stun on all special attacks. By pairing him with OG black widow, he is supposed to gain an additional 20-25% chance to stun on special attacks. If this is a flat addition, he should have a 105-110% chance to stun on special attacks. If this is a compound addition, he should have a 102-106.25% chance to stun on special attacks. In any scenario, he should be landing the stun every single time he throws a special attack unless his ability accuracy is being decreased in some way. However, this is simply not the case. He is landing the stun like 85% of the time WITH the OG black widow synergy. Without said synergy, it feels more like 60%. So either Hulk himself is bugged, or the synergy is bugged, or both, but either way, if and when it does get fixed, he better be landing that stun 100% of the time (unless he's affected by AAR at least).
If you're wondering why I'm complaining about OG Hulk of all characters being bugged, check out this video and you'll see why it's such a nuisance.
https://youtu.be/VEf4wfLSM2Y