Yes, but 30% cast time reduction translate into a very important factor.
If you follow the standard advice for the use of bd for 5min(most likely you will occasionally hardcast cb)VS;
Never miss any cb casts with bd buff for 5min(in this case you will have more cb casts off within that time frame).
Question is if its worth it or not.
Im getting annoyed that no guide i found ever looks into this.
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And that is also very true according to the general idea of playstyle/routine.
Thing is if you can cheese the last 5% out of it or not
Im used to other class forums, where people are crunching numbers. And now it got me thinking.