It's interesting to ponder where they might take it, I don't see them doing it where it increases the duration of the DoT unless they plan to change Garuda's ability but if they did do that it would be interesting.

There are three ways they could go about adjusting DoTs with spell/skill speed

Bio Potential DoT potency 240
1: Increase DoT dmg Ex. Bio goes from 40 DoT to 45 DoT for 18 seconds Potential Potency=270
2: Increase the duration of DOT Ex Bio goes from 18 seconds to 21 seconds Potency=280
3: Decrease the tick rate of DoT Ex. Bio goes from 3 sec to 2.5 second tick Potency=288

From the above 2 would be favorable, 3 would be hard to implement because of decimals and 1 could be interesting since we have these to think about.

1=Increased dmg with DoTs upon applying but it doesn't effect your current rotation meaning that you will always apply them at the same time

2=More time can be spent doing other things in that time frame, so let's say while yes it might not look like a lot but in terms of Summoner or Scholar using Ruin that extra 3 seconds in essence can amount to one more Ruin before having to apply Bio meaning that's an additional 80 damage because of change.

In the sense of 2 the combat in a sense mimics the way Ninja works cause as they stand now they have the sense of having to pause mid-combo to apply jutsu or timing a jutsu before a certain combo ends or starts.

With 1 things in essence remain the same but you'll deal more damage as the battle progresses, basically in that sense every 8 Bios would be like casting 9 Bios without the Buff which would mean every 8 Bios that would normally be a general potency of 1920 would now be 2160.

However with increases duration we have a scenario where every 6 Bios is like 7 but on top of that 6 Ruins can take the place of the time one would reapply Bio with 18 second duration meaning that amusing, 2160 dmg would be dealt however this means that Bio with increased duration would be more potent than one that just increases damage because in the above of 8 Bios 144 seconds have passed, however with 6 Bios with 21 seconds duration only 126 seconds have passed. So then you pretty much have an extra 360 potency bringing the potency to 2520 however it would have to be near perfect execution to make it pay off but it would potentially add a higher level of strategy to DoT dmg dealing.

Overall while at first I kinda liked the idea of dealing more base DoT dmg when it comes to making fights more dynamic the effect of skillspeed influencing the duration of the spell/skill sounds more enticing since it puts you into a scenario to adapt a new battle strategy based on the duration of DoT.

Cause let's say it goes both ways, if DoT duration is influenced by spell/skill speed that would make abilities like Slow even more hazardous than it is to players because it would reduce their DoT duration and force them to have to reapply it sooner.

I am definitely looking forward to whatever changes they may have in plan though since it will definitely make an interesting dynamic for NIN seeing as they have a self buff that greatly increases their skill speed/att speed.