When I just started doing leves I was totally amazed about the different things monsters in leves do.
Like the dodos who run away, or the imps who disguise themselves as dodos, or the aldgoats who hide in shiny lights and you might get lucky and won't have to fight at all, or the lvl 20 leve monsters who hide in a group of non-leve high lvl aggro monsters..
It was fun because it was all very different from the plain "Go to place X, kill 5 Y, go back to the camp, repeat."
Because with some of it, you had to put a little bit of strategy behind it.

But, as the OP said already; it's fun the first few times it happens, not when it happens EVERY. SINGLE. TIME. you do a certain leve.
I gave up on leves altogether because it's just annoying and not even fun or surprising at all if you already KNOW beforehand that it will happen.
If stuff like that happened randomly and not very often, I think it would still be cool. But not the way it is right now.
Because right now it just means "Oh god this leve again..yay, I'll have to run after a monster for 3 min now, losing exp chain bonus and a load of time I could spent on actually KILLING stuff..hm..I guess I'll just go without leves and kill those nice wild non-leve Dodos/Cactuars/etc. I've seen around the camp.."
And I doubt that's the point of leves.