Everyone needed a bit of advice on how to fight physically, whether they were a mage, warrior, assassin, or anything else. However, the same wasn't true for magic training. That's why even the mages were listening to Thala's theoretical knowledge. But listening and implementing that knowledge were two different things.
They had listened to Thala's words, but it didn't necessarily mean they would be trained in that department. Dhruv wasn't going to be overly concerned about that because he knew the more they would fight, the more battle experience they would gain. He just wants them to know where they have to focus, that's all.
Dhruv looked at the line of people in front of him and realized their number had reached at least one hundred and fifty. He didn't waste any more time and asked, "So, what do you know about casting spells?"