No-joy is just a way of giving everyone some space to begin the round. For the host it is like herding sheep, players like to drift too close and some too far away. You have to hope that everyone is trying to start on a level playing field. KOTH does promote dogfighting and furballing but both of these things are rarely "fair" you have to accept you will be "picked" or targeted, you have to get on with it and if shot down there is always another round.
Some players and wabbits in the past have tried to take advantage of it like flying towards a feared opponent calling no joy on them, so they cannot engage that person until after their first engagement with someone else. I would argue that is not in the spirit of the no-joy rule but it hasn't happened to me often.
Wabbits are just that, being one means sucking it up and preparing for everyone to come at you. Being dogpiled is an honour and usually creates some interesting multi contact fights. It is actively encouraged to hunt the wabbit (the rules differ in regards to this) in order to prolong the event. You still have to give them No Joy airspace but when fight on is called having 2-3 players attack them at the same time is fair game. Just watch your six at all times as i've witnessed some comic turn of events from god mode where opportunitist shots end up meaning the wabbit escaping and still killing everyone. I'd suggest until you see the host say wabbit or wabbits down to not go shooting the others first.