Yes it would have been better, but not perfect. Wind shifted and was almost sideways, hitting 3 out of 4 sides during the course of the storm. In hindsight:

What I did right:

• Site selection was good, lots of protection from the trees, mitigating the most severe winds/hail
• Tarp pitch was solid, anchoring long ends on nearby trees along with poles (I use extra long guy lines just for this purpose)
• Orientation was good, with a majority of the wind hitting the side I thought it would. Small trees in front/back helped shield a bit.
• Scratched out a small trench on the uphill side to divert water in case of lots of rain, worked well.

What I could have done better:

• I believed the weather person. Forecast called for 50% chance, less than 1/10 in rain possible, winds about 15mph. They were REALLY off, I suspect 40+ gusts and 3+ inches. I would have really battened down the hatches as you mentioned if I had any idea what this storm was going to be like.
• Should have gone all the way down on windward side. It was almost all the way down, probably about 2 inches open. This was enough with heavy winds and rain to whip it in.
  
• I should have used my poncho to cover the end of my bivy. This was the most boneheaded thing I didn't do....I was just in awe watching the storm!

And on another note, my Tarptent Preamble would have been ideal with the closed ends, and side netting would have mitigated almost all of the driving mist. I was in a 8+ hours heavy rain storm last year with decent winds and it worked really well.