I think the Event Bosses are WAY too hard. They have access to skills players can't get until L120+ and the item yields are crap compared to the amount of recovery items one needs to use just to win.

Either...
* Make the Event Bosses weaker, so they don't use up so many recovery items.
OR
* Make the item/experience yields better to make the loss of gold spent on used recovery items more worthwhile.
OR
* Make the Event Bosses optional, so we can fight the weaker event monsters without the risk of getting a completely KO'ed party from a boss. (The last boss even popped-up EARLY when it said second wave 31/99. It not only KO'ed my party, but also kept me from getting any participation awards. And, as I wasted over 3,000 gold on the items used in battle, I'm not too happy--which is why I won't be wasting items on Event Bosses anymore.)

I like doing the events for the experience yields of the 1-3 star creatures. However, I've come to realize the bosses are a complete waste of time/resources and will no longer waste items battling them. Course, with the way the Event Bosses suddenly pop-up without warning, there is no way to get out of it without a completely KO'ed party--which is something I'd like to avoid in the future since reviving a party of pets is quite costly in this game.

Event bosses are optional.

Just wait until its defeated.
The event is site-wide, so other players fill the defeat requirements slowly until the event finishes.

Edit: you might have massively lagged to get a jump from final wave to boss, but even then, it's extremely avoidable. Try ducking out during the last wave if you keep running into this problem.

Um... No, they are NOT optional! They just attack without warning. There is no "A boss is about to attack. Would you like to continue?" warning before the Event Boss attacks. The only sure way to avoid the Event Bosses is to skip out on events entirely--which is not an acceptable option!!!

There should be a screen directly BEFORE the Event Boss warning that the Event Boss is coming next and give us the option to either CONTINUE or RETREAT. It shouldn't be too hard. After all, we already get that option for most of the story mode battles (where the creatures are pathetically weak and it isn't even necessary)--which is why I find it frustratingly annoying when there is no Retreat option directly before an Event Boss when such an option would actually be useful.

The boss events you are talking about are in the old exploration system - which is pretty much obsolete at this point in time. When some more major features are checked off on our "to do list", the exploration system (and everything related to it) will be completely revamped. Because of this, we don't really want to spend much time fixing issues like this when we plan on completely revamping the system in the near future anyway.

So for the time being, I apologize for the inconvenience, but there isn't really anything we can do about it.