Originally Posted by
eschatological
It doesn't add ticks, necessarily. It adds damage to ticks which are already going to happen. That's what's meant when you say a DoT is "rolled into" a prior one.
IE, each ES is 3 ticks, each LnL 3 ES. First tick on first ES expires, next ES lands with 2 ticks left to tick. It'll refresh the DoT to 4 ticks (a DoT's max ticks = normal ticks + 1), the total damage of the ES is calculated as (damage from 2 ticks + damage from 3 new ticks), and then is divided by 4 for the ticks left. So even though you should have 6 ticks, you get 5, with the damage of 6. You fire the third as another tick goes off, 3 ticks remaining, 3 added. The new ES DoT is refreshed to 4 ticks, all 6 ticks are added together, and divided by 4 again, and get a new tick value.
That's why I don't understand this idea of "pro"-ness snapshotting ES on a big buff. Even though a subsequent tick of ES might be lower if you fire a lower-AP ES right after a buff falls off, it should still be preserving the damage of the old ES.
Edit: IOW, there *should be no snapshotting* of ES based on buffs. If that's untrue, I'd like to see evidence.