Because default Moon glaive, provided by Blizzard, works with tons of conditions (no orbs, no stuff, no splash etc), it was coded specially for LoD. Thats pretty good and fast system, tho not native - and there are big problem lying.
Basicly it works fine until 4+ sources appears. Then grouping, cleaning and calculations take big portion of time, causing lags on mid- and low-tier PCs.
Here we have few solutions:
1) make illusion-based skills unstackable with Glaive;
2) make restriction like "only first 3 illusions will provide bounces unless killed"
3) ignore that issue as negligible (muhahaha)
4) or something else.
Do you know something else?