Could you please define lag. Is it...
1. The game drops frames because of a computational bottleneck?
2. The game is unresponsive in multiplayer due to latency?
The trigger should not be causing 2, which is the correct definition of lag.
If you are actually referring to 1, then please elaborate. Does it happen only once or on every cast? Does it happen at the start or after the session has run for a while?
I can notice the following.
1. The ability creates units and effects. These may not be cached by the game so require loading. Loading can be slow due to the necessary file I/O. The result is a few frames are lost on the first cast. Future casts will not lose these frames as the data is cached. The solution is to create the effects and units once on map initialization as that forces them to be cached before play starts.
2. You are leaking data. Leaks degrade performance of some game operations. The result is that the ability will suffer from degraded performance over time. Removing locations will fix these leaks.
3. You are creating a variety of special effects. Depending on camera origin it is possible that these cause the graphic subsystem to take excessive time to render a frame. As a result the game is forced to display the same frame for many refreshes as the new frame is being rendered. Choosing simpler special effects would fix this (if it is even a problem in the first place).
4. You use an ability "Wailing Blast". If this ability is based off of Shadow Strike and has some field set to 0 (I forget which but it has to do with damage period), it results in an excessively high damage rate. This excessively high damage rate depletes the client of computational resources resulting in a bottleneck and thus the game having to slow down to cope. As WC3 is single threaded, the graphic rendering process may be skipped entirely for dozens of frames to try and keep game speed constant. The result may be that the game becomes a "slide show" due to excessively low frame rate for the duration of the shadow strike. Setting shadow strike properly or using another ability solves this.