I did some experimenting with my stock of 10W resistors today, and I found that I'm quite content with the brightness at 3-400mA. My current plan is to set up a three way switch with High-Off-Low brightness while I research options for making a dimming driver.
Thanks everyone for your advice and support. (I should have videoed the failing light.)
P.s. It looks like four parallel groups of leds, the way it failed.