Example:
Live: 10 second DoT deals 10k over its duration = 1000 damage per second.
PTS: 20 second DoT +33% deals 13300 over its duration = 665 damage per second.
What if they did the opposite to certain DoT's?
Alternative: 5 second DoT -33% deals 6700 over it duration = 1340 damage per second.
But here is the thing. Because it only lasts 5 seconds, now you can't just fill up on DoT's on your bar which would still result in a NET DPS loss (which is intended). However, players that wish to focus on using DoT's can do and thus DoT builds aren't wrecked. Allowing them to be still useful in trash fights and viable in PvP.
Not saying that this would be good for all DoT's, but maybe a select few of them. Ground DoT's for example.
Result is the same for parses, due to time limitation, while at the same time buffing their individual DPS which is ultimately what DoT's need.