I'm a big fan of this poem, but I feel it's acutely anti-Epicurean. "Raging against the dying of the light" brings to mind a bitter and agonising response to dying. Of course an Epicurean would hardly welcome death (beyond very specific scenarios), raging against it doesn't seem to be the most prudent response in any situation.
Love it, too, and also feel that the tone doesn't quite capture Epicurean thanatology, which triggers a reflection in my mind on Epíkouros resting in a bathtub, declaring "Remember the doctrines!"
Dylan Thomas had a turbelent life, and his pre-mature end was a bit gruesome. Prior to his death, that struggle shows in his poetry. There's a lot of despair and emotional violence there. I'm not sure how his father died, but it sounds he struggled to accept the necessary end time requires.