So I have been playing some dual wielding characters and I've noticed a couple of bugs. However, I want to mention that I am not too familiar with 5e rules, so some things may just work fine, others are definitely bugs though. English is also my 3rd language, so if there are any mistakes I apologize in advance.

1. Colossus Slayer
I've noticed that I don't always get the Colossus Slayer bonus damage when I actually should get it. So I've done some testing and I have a guess what it could be. I think the game requires you to have a bonus action in order to get the bonus damage without actually using it. I will post two videos. In the first one you can see that the target is below max health. I attack with my Offhand-Attack but I don't get the bonus damage. In the second one I do the same but instead of the Offhand-Attack I use my Main hand-Attack and I do get the bonus damage.
First Video: [video:youtube]
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Second Video: [video:youtube]
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2. Attack roll of the Offhand-Attack
In the first Colossus Slayer Video you can also see that on the Offhand-Attack I do not get my ability modifier added to the attack roll. I don't know if it is supposed to be like this or not.

3. Dual Wielder bonus AC
This one is straight forward. If you choose the Dual Wielder feat you don't get an extra +1 to your AC.
Prove: [video:youtube]
[/video]

4. Hex Offhand Attack
For some reason one doesn't get the Hex bonus damage on an Offhand-Attack. Again, I don't know if it is supposed to be like this.
Prove: [video:youtube]
[/video]

Regardless of these bugs I am still very excited about this game. It has been fantastic so far and I've already put over 230h into it. I am stoked for the full release.