Am I missing something about balance?

So I'm preparing my very first campaign with my friends. I asked them all last night if anyone wanted to hop into discord and run through a few consequence-free combats to get a feel for the system. Three people showed up with characters already done, one or two more are still working on their characters but listened in to ask questions.

First combat: 3 zombies. This was neat because one of the PCs is a Dark Blade, so a lot of his dark damage was negated. Meanwhile the Arcanist had the Arcana of the Forge, so his fire was extra useful.

Second combat: 1 drake, 2 oozes. The drake actually has a spell, so had to use MP, and it was over-leveled so it showcases a difficult fight. It inflicted statuses and stuff. Was great, great example. By the end of it, we all had a good handle on how combat works in Fabula Ultima. Then I shocked them by describing how we will also use it for social encounters.

The problem is....their very first combat took 2 rounds. 2nd combat, I took out one player, almost a second, and it was done in 3 rounds. Admittedly, the third player is an Entropist and took Accelerate. But I want to make sure I didn't mess this up.

It says in the book that combat should be like 3-4 rounds. But they really whooped those zombies. Should the Arcanist not be able to dismiss the Arcana in the same turn it was summoned? Then that second fight they won quickly, though I was able to take one down. So maybe it is balanced?

I guess I mostly just can't tell if that's balanced or not, so thought I would ask in case I missed something.

First session is on Monday. Wish me luck!