I'll also point out that my S. Burst doesn't completely trump Cloud of Daggers (which is only an OK power anyway)... CoD will still autokill a minion unless the minion somehow slides... but my S. Burst auto-damage is at end of turn, so the minion could move out of the zone.
With no feats to improve damage (but assuming a +1 weapon/implement), assuming an 18 stat, the PHB sburst deals near striker-level damage if you have 2 or more targets, even handicapping the wizard to a 55% chance to hit vs ranger 60% [using longsword, and we know that reflex is roughly equal to AC - 2.5, so we'll give the ranger an edge here] vs rogue 75% (dagger, combat advantage from stealth + deft strike).
I got SBurst at 9.35 for 2 targets, and approximately 14.0 for 3 targets.
Twin Strike with longsword is 9.54 [assuming both swings against your quarry]
Deft Strike 10.875
For comparison, a fighter's melee basic attack (again with a longsword, 60% to hit) is 5.7.
So I'm not nuts about adding damage to SBurst without taking some away, although I have talked to players who say they'd rather have 1d6+int and no control effect and just deal a lot of damage. (Personally I think they just want to be strikers.) Another comment was that the enemies could easily avoid the extra damge, to which my reply is that you at least force the enemies to move, and if you're lucky/smart/teamwork, you make them take an OA or waste their entire move shifting.
Your calculations seems off.
9.35 is the number you get if you don't take account the critical damage. The number you really are looking for is 9.6dpr.
I could try to check all your numbers but here is the main thing you have to see with this. Wizards have a grand total of 1 feat they can choose in the heroic tier that add damage. Rogues, Rangers, Fighters, etc, all have 3, 4 and 5 feats they can choose. Each of those feat add 0.5 to 1dpr. You do the calculation.
For rangers, just going from using a longsword to a bastard sword is a 1.3 DPR increase with twin shots once you factor everything else.
Hunter quarry to D8 is nearly 0.9 dpr increase with twin shots.
Weapon focus = 1.2 dpr increase with twin shots.
Two Weapon Fighting = 0.6 dpr increase.
The same is true for rogues, etc.
The wizard got only 1 feat, weapon focus with staff or one of the thing that add to damage with a type of damage and those 2 don't stack anyway.
That feat will add 1.1 dpr with 2 targets, 0.55 dpr with one. But that's it.
I mean let's say we have something like a "GreatStaff of Whatever" that requires 1 feat, that staff is a weapon that increase all spells die by 1 category. D6 become D8, etc. That's 1.2 dpr increase with 2 targets, 0.6 with one, etc.
We could probably create tons of feat to give choices to wizard equivalent to the other classes but somehow the creators of the game decided that in the player's handbook wizard feats should be sparse and far between. Unless they count each individual feat like Raging Storm, Astral Fire, etc, to be "different" but none of them stack anyway.
That's one of the main reason wizards cannot hope to touch striker dpr atm.