So I'm running a stopwatch built into the code, basically starts right as the spell begins casting, and stops at the end of the sequence. The Timer priority for the spell timer is 50 milliseconds, so basically, the spell can be up to 50ms late, or 1/20th of a second. At timer priority set to every tick (no delay in tick checks), its hitting from on time to +4 ms, which would be virtually unnoticeable. 50ms would be pretty unnoticeable, as well.
Which brings us to EA. After running 100 circle 1 spells, the average cast time is 1.012 seconds. The problem is, some of the spells show (EasyUO program) as a .9 second cast time. Unfortunately, the highest resolution time EasyUO shows is tenths of a second, so that .9 could easily be .99, or just .90. Thats a big difference. Now, with EA, I'm seeing .9 to 1.1 second cast time, so that could be 1.1 second, or 2 seconds difference. None the less, I am almost certainly convinced EA slightly lowers the cast time (which would explain the .9 second cast time, even with 74+ ping), maybe to make up time for their own timer resolution.