I do two types of regen for some of my newer bosses, nothing advanced though. Just a cleaver trick where you set the boss to start with the poison attribute and he absorbs poison so that he's gets a boost in HP. I first did this back in 2009 or so with my Eve of Darkness hack where you fight Warmech.
Look here at 3:05.
[youtube]http://www.youtube.com/watch?v=yjbxSGcJPq4[/youtube]
Look here at 3:05.
[youtube]http://www.youtube.com/watch?v=yjbxSGcJPq4[/youtube]