It's not a bug but it should probably be changed, or if it stays low duration, should at least drain more HP. For example, if the Drain effect was 15 + Character LV, it would add up to the extra 30 of the missed turn over 2 rounds.
45 > 45 = 90
vs
30 > 30 > 30 = 90
Math!
45 > 45 = 90
vs
30 > 30 > 30 = 90
Math!