Thunderwave and Gust of Wave and Gust of Wind are both available on scrolls in the starting areas as well as being learnable spells to several classes. Fire bombs are all over the place to find. Its possible you can hit that fight unprepared (and even then a strong group on normal diff can beat it with luck) but you practically have to beeline for it and ignore everything else out in the starting area for that to happen. Similar to just walking straight to the Hag's hut and picking a fight with her right out of the gate, you have to be completely reckless to get into that situation. And the spider fight has some pretty obvious clues on how they want you do do that fight and the only real monkey wrench are the Phase spiders, if they land poison or double gank a squishy character. Someone with limited game mechanic knowledge and zero idea whats coming is going to get taken behind the woodshed, but thats who the easier difficulties are for.
That's the thing. At lvl 3 you don't have a lot of this shit unless you planned for it and knew what was coming in advance