Ilbranteloth
Explorer
But you still GOT a new spell slot. So if not flaming sphere then odds are another damage spell. On the other hand, a frontline fighter who rolls a few 1's for their early HP is severely hampered in doing their desired function. HP are a character resource. They shouldn't be randomly determined.
Actually, at least the way we play and which is RAW in AD&D, after the group of spells at 1st level, all of the spells you gained are ones you found. So no, it's not "odds are another damage spell." Unless you choose to wait until another damage spell.
As for what "should" be randomly determined? I think that's a decision made by the designers and/or the group. We prefer things that are outside of your control to be randomly determined. That includes stats, hit points, etc. You can choose to expend resources and training (feats) to gain more, but in terms of the base amount, that's the nature of the world.
And no, we haven't found low hit point fighters to be severely hampered. They generally go about their job a bit differently, but they still get the job done. A fighter with lower hit points might opt for heavier armor, a shield, and longer weapons, and use different tactics, that's all.