I thought it was more her strength limit. When she did all that in the field, she needed to recover, hence Nynaeve medicating her in Shadar Logoth.

So I think it's wrong to think Moiraine is somehow constrained to a few-on-one dynamic with the Trollocs. She can absolutely take on a band or two, given the right conditions, and end them in a few moments. That holds up based on everything else from the books, too. Agelmar saying that a single Sister is worth a 1000 lances isn't wrong. If anything, it is an understatement, in a situation where the Aes Sedai is just facing an advancing army head-on and can simply unleash slaughter. We saw that with the Aes Sedai who kidnapped Rand against the Shaido. They absolutely had that very large army stalled before Rand started thinning their numbers. And the Whitecloak camp was more of a distraction than firing for effect, so she wouldn't need to use as much effort to control it.

Which is more or less what I said. But doing it one at a time, constrained as she is by line of sight, would take too much effort and wear her out. As long as it's no more than you think it is. Of course the trailer is going to make it all seem a lot more dramatic and over the top, but the way this thing has been promoted, they're going all in on Moiraine the Badass. They seem to be of the school of thought that she's the unsung hero, rather than an antagonist who eventually reforms, and who is, for all her good character traits, not super competent at anything other than channeling and intrigue. Her most important character moment is when she is forced to confront the fact that she is not in charge, she is not the hero and it is not her fight to win. Running with the Tumblr fangirl BESTEST HEROINE EVAR ball is just going to distort the story.