We are in SF Bay between GG and Alcatraz. Current can be a factor, but we try to account for that. I am measuring total heading difference and dividing by two. So for instance this weekend we were going from a heading of 160 to 270 and then back to 160. We were at slack condition, with winds 20+ mph with some higher gusts.
What I am suspecting is the mast is raked too far aft. When you look up at it, the rake is very significant, I estimate maybe 12 inches.
You may want to check your compass with a hand-bearing compass.
The mounted compass can be off a lot.
Also I like to check with a track from the gps
With wind that strong I have never been able to get a 90 degree tack. Of course I almost always have current.
When the wind is strong free-board and sideways slippage is worse.
Waves are a factor that can cause you to loose points too.
What condition are your sails?
How much were you healing. If more than a few degrees reefing will actually improve your pointing.