Badge challenge? I think I got the badge the moment I bumped into Manticore, not after I managed to win the fight.
And wouldn't it be more expected for people to not know what they're getting into? I mean, it certainly wasn't an insurmountable challenge but at the time I had been avoiding grabbing Bile (and thus continuing the mission) in order to go back and explore the prison cell areas I had bypassed previously. If I could suggest anything it would be to predicate the big 'optional' fight's appearance on after the player has gotten Bile his arm back. That was when the additional Wyvern mooks spawned, so I don't think it'd be hard to include the ambush as well.
I'm not really arguing against an EB ambush, anyway. I know it exists elsewhere. It's just that /three/ of them was an unwelcome, unprecedented surprise.
