While i do agree on the timer ones (i like having less numbers too), the exclamation point and health bars would need visual representations. On trolls for example the alert and spotted behaviors are very similar.

And about the boat:

1- i like the visuals just as you, so i would like to appreciate them without the worry of crashing my boat because i didn't know that my character was turning.

2- on open seas with fog i cant see any reference that i'm turning except for the minimap but i would definetly feel the weigh of the helm. Therefore i still think the visual indicator is a must because, like you said, i need to see where i'm going and not looking at my boat's rudder all the time.

One way that they could compromise is add as default the fade away the icons. They would appear again if the wind is against you or in favour for a brief time, and the helm could fade away if the player is not making turns.

And honestly the fade away icon could apply to many things like the hungry timer, the enemy health bars... I mean, the stamina bar already does that.

I do think the timers should stay for potions like freeze and poison resistance though.