Destil
Explorer
Hybrid Slayer will be a tricky one for them to figure, I suspect. Same for all the "I'm barely more than a melee basic" classes.
Got to make sure a hybrid executioner / slayer isn't just a slayer with an extra d8 per tier damage, for example.
Yeah, there's plenty of stuff to look over here, but as far as feedback making sure that you can't double dip something like Slayer/Thief is the most important thing to get right. Unifying all the 'basic attack bonus' features somehow and forcing the hybrid to choose one and only one would be the best way to make it work, I think.