Definitely the scheduler and letter writer are two of the weaknesses especially for specialists. Granted, for straightforward scheduling and letter writer, they work great. But being able to adapt them to your particular practice is the difficult part. That's a basic problem with most EMRs in my opinion. If you try to be everything for everybody, they end up so bulky that they are miserable to use.
The only way that I know of to block more than 3 hours is to manually go, week by week, and manually select the column on the very left of the schedule, click where you want the block to start, hold shift, click where you want the block to end, then click the "block" box at the top. Again, it's tedious if you need your block to be longer than 3 hours, but doable.
I've said this before, but Microsoft Word is the epitome of great software. Very simple to use for basic things but has the ability to be very complex for those with more demanding needs without being obtrusive. Need to be more like Word.