This is sketchy at best. I have known several players to get banned for attacking high end mobs by being in a place where the mob cannot attack the player. The boat deal sort of falls into that category as well. Is this an official greenlight that this type of tactic is now ok?
I can't comment on what may have happened in the past with the players you are talking about or what may or may not happen if you'd try and exploit something elsewhere, but will say that for this content the use of unconventional tactics to get the upper hand is encouraged. The idea, after all, is to defend the cities! The quicker that goal is met the more and more m'arties you'll have to hand over to the King's agents!
