I do things even more simple. Wind from the left = 5 degrees correction to the left and vice versa. Regardless of actual crosswind component or wind speed.
What you need to realize is that when doing a diversion, you're not going to do that using dead reckoning. Instead, you're going to ask ATC for vectors, use radio navigation or feature crawl. All offer plenty opportunity to correct the initial guesstimate of 5 degrees.
Likewise, my thumb is 10 miles which equals five minutes. 4.5 minutes for a tail wind, 5.5 minutes for a head wind, regardless of strength. Revise halfway through the diversion as required.