I don't think that the rules for the event and the actual game play are the same.
Rules indicate "huge VP bonus" for killing epic monster. I have killed up to 3 of em in one battle but get no more (sometimes less) VP than when no epics show up at all. Also, rules state that VP is doubled when an entire stage is completed. I believe this was in place in the very first slayer event, but does not appear to be the case now.
Lastly, it is stated that sometimes gold and relics are dropped. Never seen that in my million+ times playing.
A final comment: watching a video to get energy restored seems so....well, ..,random. Some of my guildies get recharged constantly, while others (me) see that opportunity rarely. Well, I see it all the time, but it always comes back and says no videos are available. What is the criteria to get the restoration?