You actually gain more dps to let the dot on goring do it's full length than to just spam that.
Only 40 pot difference from rage to goring each hit. Goring dot is 85 pot over 21s. 85x21 = 1785/3 = 595.
Over 21s assuming gcd of 2.5s is 21/2.5 = 8.4. so baseline you will do about 8 gcds in the time the dot ticks. Takes 3 gcd to hit goring, so 2 goring over 21s for only 40x3 = 120 potency.
595 > 120, assuming my maths aren't wrong since I'm not super mathy