Sorry, that does not fly with me. They have the mimic event where you can go talk to an NPC and it turns the event off for you. If they wanted to let people opt out of this, they could have done that here too.
Could they? These are monster champions we're talking about - they're determined automatically by the game. Mimic Hunt works with that system because Mimics can only appear whenever
players perform a specific action (opening a chest). For this, though, the champions are assigned when the quest loads, so if a non-event player and an event player are in the same party, you could end up with all sorts of problems.
Anecdotally from the U63 Lamannia previews, the champions in question are a pain to deal with, so putting them in Reaper only makes a fair amount of sense - the event would be very unpopular indeed if it made life difficult for people in heroics to unlock quests in a level range they're nowhere near.
If you're not someone who plays on Reaper but don't want to miss out on the event, pick a popular quest at your level range and put up an R1 LFM for it. Chances are you'll find at least a couple of people who can help you out with it.