The thrown projectiles blowing up is an annoying one as well. They de-spawn after a certain distance, but if they hit a reflect right around that time, instead of either de-spawning or bouncing, they explode. Some of my builds have reflects is seemingly weird places to try to avoid it.
For the crystal blowing up, what I've seen a few times is ranged, mostly wizzards or whatever they are, will shoot over a wall at it. But I've also had one blow up with nothing but a warrior near it, and they aren't supposed to be able to attack it.