Are low level casters underpowered?
IMO, no, low level casters aren't underpowered.
They are very aware of their own mortality.
The 1st lvl Magician boils water because it's less likely to put him into a coma. Fighters can fumble, but not when they put on their armor or remove a helmet.
Mages can do combat, control, defense, elements, weather, brew tea, construction, research, Google, wiki & tweet with the best of them.
Yet, each one of these can kill a mage. The less-skilled make tea and throw it at their enemies. If they try any more, opening a magic rift or bursting into flames are around the corner.