A small correction: Fire Arrow and Ring of Fire don't always share the amount of damage ticks at at skill level x. They just happen to have the same amount of ticks at skill level 130. Actually as you can see if you pay very close attention to the vid, at skill lvl 150 RoF would have 1 additional tick vs FA. A curiousity I left out of the vid: The beneficial debuffs of fire spec actually tick away at the same rate as the dmg. So increasing fire speed actually makes this part of the skills worse. This was addressed on one of the live streams and is not a bug but something the devs have decided to live with due to performance implications of separating the math.