Redstone propagates through dispensers and stops hopper

Please provide a screenshot of your redstone setup.

Just use normal redstone dust, I don't see any problem in that. I don't consider it a bug.

I can't get the attach screenshot function to work. Anyway, I have a way of making a clock so fast that it basically acts like this torch and stays on all the time. But because the signal propagates to the hopper from this direction and from below I'm unable to make it fire quickly because it keeps the hopper from draining efficiently.

This is working as intended. A dispenser is a solid block, thus powering it directly by pointing redstone dust at it makes it power adjacent blocks. If you do not want to do that, simply power any nearby blocks connected to the dispenser instead.