Alas not everyone has a static ; for people going in PF, it is useful to know quickly if you're wasting your time cause you're about to hit enrage everytime. Sometimes failure isn't visible at naked eye.

Let's say for instance. You miraculously find a team that does mechanics approximately ok (trust me it's a miracle, mechanic dealing in so called "kill groups" is a complete lie). So you have a CHANCE at killing. One DPS is pulling a 4k. 6k is required for each DPS, with tanks doing 4k and heals doing 2k.

No way 2k can be caught up by the other 7. Well you are bound to hit enrage. Knowing that, will you happily spend 3 hours knowing perfectly it won't lead anywhere ? I will not. When you reach kill level (mechanically) in hours, you don't want to be spending 3 hours in vain again, and again, and again, that adds up to 2-3 weeks later, still not down, all while you know the fight after a timer (thinking of O9S). Someone not going in PF cannot understand the pain of this "roulette". I'm no top player, YET I felt that pain.

Now there are people who will trash talk, or shame and replace and I am absolutely opposed to that. But seeing that, you can just politely walk out of there and not waste 3 hours. And I'm saying that knowing sometimes it will be me the deadweight. If we wipe at 2% and nobody died and I'm under them, I'm the one wasting 7 people time.

So indeed it is absolutely not needed to kill, but it helps a great deal analyzing what goes wrong.Or say if your group is just missing 800 rDPS then watching some logs can help you know how they maintain better uptime than you.