This is a comment on the design of the Sorcerer in Dungeons and Dragons, not specifically the DDO sorcerer because DDO just based their design on the D&D books. I'm being more philosophical than anything.
I don't understand why the Sorcerer has such a crappy hit-die. The sorcerer is described (in the actual source material for both D&D 2.0 and 3.5) as an arcane spell-caster that travels and explores the world. This is even reflected in the original artwork in those books. Shouldn't someone who is out in the world adventuring have a higher hit-die?
To quote the 3.5 PHB:
On the other hand a Wizard (previously magic-user) is an acadmeic who prefers digging through books, studying, and experimenting with magic. This nicely explains why the wizard gets more feats and spells and prepares spells. it also explains why the wizard has a d4 hit-die. The wizard is a professor who only goes out into the world to chase down some academic curiosity while the sorcerer explores and travels.The typical sorcerer adventures in order to improve his abilities. Only by testing his limits can he expand them.
Another quote from 3.5 PHB:
Even more so, the cleric has just as many spell points and spells as the wizard but gets a better hit-die, is able to wear armor, and knows how to use more weapons. Yet the cleric is really a religious type. Arguably a sort of traveling missionary bringing faith and healing to those who are not yet blessed by the faith. I don't understand why they get heavy armor (they are not knights of the church, the knights would be the paladins, but that's another argument). The point being, there is prescience with this spell-caster type to have a higher hit-die and more weapon proficiencies.Wizards depend on intensive study to create their magic. They examine musty old tomes, debate magical theory with their peers, and practice minor magics whenever they can.
Even the favored soul (which I don't have in my books) has more weapon proficiencies and a better hit-die but is basically the religious version of the sorcerer (more spell points, less feats, less flexibility in spells).
So, other than tradition, why doesn't the Sorcerer have a higher hit-die and more weapon proficiencies. Even light-armor proficiency would make a lot of sense from the point of view of the intend flavor of the class.
I'm not suggesting Turbine change the sorcerer because it might unbalance the game and this isn't about game mechanics. It's about the flavor of the game.