Hey, thanks for the comment!
I like to describe how the enemy are trying to hit the players and let them describe how they are avoiding it (so they can use positioning, group tactics and items to gain more dice). And them I let them make their attacks in the same way. And unless their are surprised, players always go first.
For bosses I use 4 to 7 hearts.
But as always, feel free to adapt as you see fit. Hope you have fun!