FormerlyHemlock
Hero
Makes sense to me. Feels fiddlier than I prefer (liked a slightly souped-up and fiddlier version of the 5'-step, which I actually find Disengage to be a more elegant solution to; and in particular a neat tool in the Rogue's toolbox) but sounds like it works a lot better than I initial perception of it.
Note that the Rogue still has the same capabilities under this rule (in most situations) that he would in vanilla 5E.
bonus action Disengage = (30' movement, no opportunity attacks) = bonus action Dash + move backwards
The only time the rogue suffers is if the Rogue wants to use his bonus action to Dash and his regular action to Disengage (or vice-versa), in which case this rule makes him run 45' backwards instead of 60', because double-Dashing isn't multiplicative under 5E rules.