I like this idea from Tobold blogs from the hip – WoW Insider:
“Every boss in the raid dungeon gets between two and five random boss abilities, with no way to find out what the boss does except for fighting him.” I think it would make instancing and raiding a lot more interesting if bosses were more unpredictable. The downside would be that some of the more interesting scripted encounters would be taken out. Mind you even the most interesting scripted encounter gets dull after a couple times through.