Hey all. I do know there is a global cooldown that you must also account for when setting /Delay

IE: /Cast smite *Which has a 2 second casting time* your delay would be 2 seconds for the cast plus 1 second for global cooldown plus latency variable ussually .2 to .8

So 2+1+.8 = /Delay 3.8

For me my magic latency number is .6.

When using insta spells / attacks I use the Global cooldown + a slightly higher latency variable like .8

This seems to work well for me when on both main and boxed toon.

Hope this helps you