Damage over time is inconsistent and very misleading. Bugs abound like thunderlords etc.

Certain dot spells will proc immediately and other will delay before doing the first tick. There needs to be some clarity and consistency with this game mechanic as it is very misleading and causes miscalculations on the part of the players and on the part of the server code.

Example 1: Morganna pool with proc thunderlords almost instantly because it's dot tick is NOT 1 second. It will also tick outside of the pool as it delays it's last tick based on certain spaghetti that is unknown. This is well documented.

Example 2: Velkoz and Anivia dot will proc once early and then delay for a sustained period greater than 1 second before the next tick. The damage is then readded and you'll see nonlinear behavior in the game (if it even bothers to calculate and show it correctly. This also well documented on many youtube channels.

There are many more examples and a cursory browse of the internet for examples of Riot spaghetti code and dot will net you fine samples of the shit Riot produces.

Riot, please take the time to work on this issue as it's driving many people away from the game.