Watch alarm now seems weak
I have a Watch S2 with 4.3.1.  I haven't noticed any changes during my alarms or notifications.

Check to make sure your haptic strength has not been accidentally lowered:


Open the Watch app.
On the My Watch tab, tap Sounds &amp; Haptics.
Scroll down to Haptic Strength.  Is it in its normal position?  To make is stronger, move the slider to the right.  
For even stronger haptics, turn on Prominent Haptic.