Wrong. Absolutely, unequivocally wrong. It is defined by the only valid source of 4e Class information in existence. You are in a hopeless state of denial to think that the PHB cannot define something it created. Whether or not it plays out in the game is irrelevant. Game play has nothing to do with definitions. Game play is indicative of how well the developers followed those definitions during the design process.
So basically you are saying that your description is useless. Well, thanks for being useless.
Also, please tell me whether or not high damage is valuable or high frequency, noting that the description does not differentiate and high frequency is what is valuable against minions and well, everything else.
Also wrong. Flame Strike does 2D10+Wis plus an additional 5+Wis in ongoing damage. A Wizard spell won't do equivalent damage for another 6 levels with Prismatic Burst. That's a long time to play catch-up. It starts at 9th level and doesn't stop. Next it's Firestorm. Finally, Astral Storm. Pure damage goes to Clerics. Flame Strike average damage scales higher because some developer thought it would be a good idea to incorporate Attack Stat + Implement Damage with ongoing effects.
Besides Prismatic Burst doing much more damage than Flame Strike you might want to look at fire burst(lvl 7 encounter power), Winters Wrath(lvl 7 encounter), wall of motherfreaking fire(lvl 9 daily that does 3d6+int/round OR MORE with NO SAVE ENDS), Stinking Cloud(lvl 5 daily that does 1d10+int TWICE and continues to do so ongoing with NO SAVE ENDS), or Force Orb(lv 1 Encounter)
Lets use a level 5 daily since comparing it to wall of fire will just be unfair(3d6+int whenever they enter and at the start of their turn and their movement costs 3 squares AND the wizard has an at will knockback at his disposal? Ah ha ha ha ha ha ha ha ha that is 36 average damage on one round, let alone any further ones)
A hit with Stinking Cloud is 2d10[avg 11]+12 damage for 33 average damage(on the first round), A miss is 1d10+6 damage on the first round.
Second round its another 1d10+6, third round its another 1d10+6...
So if we assume that attacks are hitting(since your cleric said average of 33 damage and not an average of half that) and we average over 3 rounds(saves) where your guy averages 2 failed saves(which is a bit better than he would actually be doing since you don't have access to spell focus). Then Flame Strike does 33 average damage and Stinking Cloud averages 46 damage over that period.
If we figure a 50% hit rate then Flame Strike averages 21.5 damage and Stinking Cloud averages 40.25. Nearly
twice as much before we figure that Stinking Cloud won't end until someone stuns the wizard. ED: Oh, and i can move the Stinking Cloud around to damage more enemies(and they will get hit twice on that move when they enter the zone, and when they start their turn in the zone increasing my damage farther)
Oh, and before you bring out Blade barrier, remember that ongoing damage of the same type does not stack, only the most damaging one applies, remember that blade barrier does not deal damage to adjacent enemies, remember that blade barrier is twice as easy to cross as a wall of flame, covers 3 less squares(I.E. wall of fire has 3 more squares to place before its extra damage on adjacent enemies), and doesn't block line of sight.