Usually find the opposite is true. Tanks rushing through, not waiting for people to explain mechanics. Then, once the group wipes (which will happen when not everyone knows the mechanics...) they pull again immediately. This happened to one of my groups in Alexander 4 yesterday and it's infuriating. The content has been out less than a day. Not everyone is gonna know what to do. Hell, that text that pops up at the beginning, the one telling you that you are getting extra tomes? That's not a "you're super special!" gift. It's because someone has never seen this content before.
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As for the topic at hand, what other people said:
- Personal cooldowns
- TP/MP regen
Other possibilities include:
- Looking up notes/quick video on the fight (if they've only done it once or twice if not entirely new)
- Some random IRL thing (they get away with this because what are you gonna do? Pull without them?)