So in answer to my question:
"So did I miss something big that makes Sorcerers more powerful DPR or are Sorcerers relegated to buffer/rpg roles using subtle spell etc? How do you use Sorcerers? (I do understand that Sorcerers DPR is not bad, just that I question there role when compared to Evocation Wizards.)"
I seems like it boils down to 3 things.
1. Evocation Wizards are not as powerful as I thought because I miss read some things. Worsened by the fact they get a lot of there power later when casting a level 5 cold of cone at max damage is over shadowed by the ability to cast level 7 Fire Storm for example.
It is illegal to Overchannel a spell over 5th level. Meteor Swarm is not eligible for Overchannel.
Just a quick correction I believe:
It is the Necrotic damage backlash that the caster takes that ignores resistance and immunities, not the damage of the overchannelled spell.
Its nice as a one-off ability, but dangerous to try to use regularly.
While a lot of damaging spells are evocation, there are enough effective spells of other schools to make the sorcerer's metamagics like careful spell still effective in comparison.
2. While Sorcerers CAN DPR they seem to be better suited for a roles of crowd control and buffing. Thought it could be (had has been here) argued that this is more of a happy accident then an intended design and as such makes it less apparent to many players. This "accidental" design vs the implied design (Which is how I took it, hints this whole discussion) can lead to players accidently taking "trap" chooses.
Careful Spell is kind of awesome when combined with crowd control spells like Web and Stinking Cloud, or Evard's Black Tentacles if you somehow manage to get it. It's worth noting that it guarantees successful saves against that spell--for as long as it lasts, not just one round. That essentially turns the spell's AoE into extremely hostile terrain for your enemies: while they are stumbling through the difficult terrain of your Web spell, getting stuck in the webs frequently and having to waste actions to break free, your melee bruisers get to freely attack every turn, even the fighters with a Dex save of -4, while your ranged sharpshooters can just hang back behind them and plug the enemy full of arrows, again without penalty.
Quicken is obviously the best and most versatile metamagic, with Twin and Careful all tying for second place in my mind. (Extended excels in one niche application: doubling the healing a Paladin/Sorcerer gets from Aura of Vitality. It's worth taking for that alone, if you think you'll ever have access to that spell.)
And elemental based subclasses, and class abilities that, at first look, seem to favor blasting (empower, quicken, careful, twin). However, the entire class functions best when not used at face value: careful works best with crowd control, twin works best with buffing, you should almost never create spell slots with sorcery points and instead burn low level slots to power metamagic on your higher slots, etc. For a class that has a narrow list and abilities that seem custom made to empower blasting, the sorcerer doesn't really deliver over the other casting classes.
Also, there's a lot of trap choices in the sorcerer class -- both in spell selection, metamagic selection, and subclass selection. Picking black as your dragonblood color, for instance, is bad. Picking subtle is very limited except in certain game styles. Knowing that you should probably skip picking up a blasting spell of your color (provided your red or white) every level and instead up-cast lower level spell and pick up some variety is another.
Can you have a successful sorcerer? Absolutely. But it's a lot easier to not have one with the class setup than to have one. You have to really grok the weirdness of the class to have a solid sorcerer. This is shown out by most people's examples of great sorcerers focusing on buffing or CC and not straight up blasting, which is what the 3.x iteration excelled at and is, at first blush, what the 5e version appears to excel at.
So don't let your "Draconic origin" control your spell selection.
Crowd control with Careful Spell:
- Sleep (reduce the number of enemies effected to make it more effective against stronger opponents and more useful at higher levels)
- Web, Stinking Cloud, Reverse Gravity, Cloudkill to lock down some bad guys so you can beat on them... Though I should point out Evocation Wizards can do this too.
Duel Buff with twinned: Jump, Enhance Ability, Enlarge/Reduce, Invisibility, Levitate, spider climb, Fly, Gaseous Form, Haste, Protection from Energy
Duel Debuff with twinned: Frostbite, True Strike, Blindness/Deafness, Enlarge/Reduce, Eyebite, True seeing
Duel Damage with twinned: Firebolt, Witchbolt, Ice Knife (maybe, ask your GM), Ray of Sickness, Phantasmal Force, Blight, Disintegrate, Finger of Death, Power Word Stun, Power Word Kill
Duel Crowd Control with twinned: Hold Person, Hold person, Dominate Person, Telekinesis, Dominate Monster
Though I am sure I missed a few.
3. Sorcerers maybe limited in spells but make better use of them through things like action manipulation (quickenned spell) and the fact that Carefull spell and empowered spell meta magic's work at spell levels higher than 5 and on a larger variety of spells.
The sorcerer may not deal as much damage using a single spell as a wizard, but he honestly doesn't need to. Quickened Metamagic is just that good.
In one session a few weeks ago, my group came under attack by a team of Derro assassins.
My position on the grid was not advantageous, so I took the disengage action to avoid provoking an attack of opportunity from three Derro moved over 10 feet and unleashed quickened Cone of Cold, hitting and killing 12 derro instead of just 5 if I had remained where I was.
If I had been a Wizard, I would have had to take 3 attacks of opportunity to pull off this same tactic.