Of course that red dragon sorcerer is going to be ineffective against anything that has resistance to fire. Poison vs. Anything undead. Etc. So some sort of backup is nice.
Well, except for the ability to bypass energy damage resistance that's built right into the class.
Me, I think that "I'm dragon-themed, which means I use a color-coded energy scheme" is dumb. There's just more to a Red dragon than it's firey breath. It's got claws and teeth, wings, immense strength and personality. Why no Fear Aura-style spell? What about great rending claws as a physical attack? What about a roar that shatters things?
Great! Those things should be included too! Just don't have me select a dragon type, give me an energy resistance to that energy type, and
then give me no mechanical incentive whatsoever to choose more than a trivial number of attacks that actually use the dragon theme that I selected. I'd rather you didn't give me a dragon type at all than to give me one and then promptly ignore it. Lets say I choose to base my dragon sorcerer off of green dragons. I get poison resist 5, which is nice but doesn't encourage the use of poison attacks. I get the ability to bypass up to 5 points of Resist Poison X, which helps, but really only removes the normal penalty of specialization.
What I
do not get is even a
single at will or encounter poison attack at level 1. By design, my green dragon themed dragon sorcerer with the special poison powers is going to be spending his time breathing fire and cold and lightning, whether I like it or not.
Even if I had chosen a more common dragon color, the basic problem remains. You spend a lot of your time outside of your theme. If that's going to happen, either change the theme, or don't give me a theme at all.
The best example of how to AVOID this flaw in a class is the warlock. Every warlock build has a lot going for it, but everything fits within the theme of the pact. No warlock is restricted to just powers from their pact, so the theme isn't mandatory, but its there. Contrast this with the "pick a suite of energy spells" design of the other arcane classes, and the difference should be clear.
I just really hate classes that boil down to "pick a suite of disparate spells with no thematic connection betwixt them." Hate, hate, hate. The energy type issue is just one way in which this surfaces.