Delayed blast fireball average damage is 49 and takes 6.5 seconds (rounds) to cast also it can be resisted for half damage so 75% of that is 36.75 divided by rounds (6.5) gives an average damage per round of 5.65 and if modified by enhancements and items to +90% it can go as high as 10.74
A level 14 fighter with comparable strength (to a mages Intelligence) gets +10 hit and damage. If using a normal longsword and attacking three times per round and hitting only half the time without considering enhancements or feats they would average 21.75 damage per round. (4.5 damage average + 10 for strength (14.5) times 1.5 (hitting half the time) =21.75)
While it is true that wizards can kill certain monsters weak to certain effects easily by maximizing + empowering and blasting, in general they cannot kill normal monsters with normal damage spells except for a few select instant cast ones and even then they require more than 10% of their Mana to kill them
Currently casters prefer persistant or effect spells but not direct damage unless using both maximise and empower. This is because they cause low damage and are very slow. Killing a creature of the same cr level as the caster takes a huge chunk of mana (20% or more) and causes intense aggro which most casters cannot handle because of current long cast times. In pnp all spells can be cast within a single round (1 segment per level or .1 seconds per level ddo time) which allows for only a few concentration checks. casting a spell like acid fog would allow at least 5 attack on a low armor class character with low hit points usually resulting in at least one concentration failure even with stoneskin on (at uper levels).
Is this what DDO wants for wizards and sorceres? are they just buffers/debuffers/persistant and instant death casters? can fireball/lightning bolt and delayed blast fireball be made the prefered spell of casters again? I would love to be able to cast these at a creature and have it go off before the fighters with thier massive dps destroy the thing. Of course my mage can power up and take out up to four fire reavers at higher levels but then thats all he has left and a fighter with protect fire can do much better. Wizards in dungeons and dragons were made to be able to do high damage for a limited time and in DDO that doesn't happen, Devs please take a look at actuall DPS and see if you can put mages on a higher level by shortening cast times to a single round or less (even if recharge is a bit longer) and upping enhancement boost to a level that exceds that of fighter types making our direct damage spells something impressive.