I'm just wondering why Broodlings run away from Dark Templars when they get hit. I have a trigger that allows vision for the player with the DT, and the Broodlings attack only until they get struck back by the DT, then they run back. Is there any way to resolve this?

Never heard of that. video?

I know I've definitely seen it in a couple of maps I made, but I can't seem to find an example at the moment.

However, I have a second question, so may as well use this post. Does anyone know of a way to create Vespene Tanks in a game? I basically need an infinite supply of these, and the 'Create Units' trigger doesn't seem to work.

You can't create them. You can only pre-place them and move them around.

because they are preplaced, you can detect when they are low on HP and move them away before they die.