For argument sakes, I parsed some numbers to illustrate how the wizard's DPR can be kept in check in relation to the fighter. I'll operate off of the following premise: the fighter should be the best (well, one of the best) for single target DPR, and the wizard should be an excellent utility that shines against multiple targets. With that in mind, I'm going to look at the potential single target DPR for each class. The goal is to create damage guidelines that keep the wizard from overtaking the fighter in this arena.
First, I broke the fighter and the wizard down by level. The DPR numbers for the fighter are derived from the average value of a 1d8 and 2d6 weapon wielding fighter. It includes the critical damage gained by level and expertise progression of the current fighter. I removed the strength bonus from the fighter; this is due to some hints from the developer. In addition, the fighter's DPR is calculated off of a 65% hit chance. I can adjust these number if it is required at a later date.
Second, I changed the wizard's spell progression in the playtest package. The reader can figure out the progression from the table below. The main reason for this change is due to the developer's statement that wizard's will be getting three slots per spell level in the future packet. In addition, the numbers for the at-will spells do scale; however, I kept them at 75% of the fighter's DPR at that level. The wizard is capable of the nova phenomenon and a lower at-will setting takes this into account. In addition, spells are rated at 75% of their actual spell power. This is due to saving throws. Half of the time an opponent will take full damage; the other half of the time, the opponent will take half damage. This equals to 75% of the entire time. In addition, I removed lower level spells from the higher level casters. If the spell's DPR is lower than the at-will DPR, it would lower the overall DPR of the wizard. This would not give an accurate assessment.
Third, I created two tables. The first table details the math. It's results told me what numbers to plug into the second table.
The first table is broken down by damage (minimum (1d8) and maximum (2d6) of the fighter is here with the wizard at 75% of the fighter), rounds designate the average number of rounds for an adventuring day (based on statements by the developers), the average details the average of the minimum and maximum damage, the total amount of damage details the amount of average damage dealt during the adventuring day, the difference represents the difference between the fighter and wizard, the number slots is the maximum number of effective spell slots of a wizard (I assumed six (three for each of the higest level spells), the second average details how much more damage the slots need to do for to get the wizard's damage up to the fighter, the high level average adds the at-will and average difference to details how much damage a high level spell needs to do, the calculated DPR is a checksum to make sure that the damage adds up over the adventuring day and the final column details how many slots the actual wizard should have based on a three slots per spell level. Here's the breakdown:
This just gave me a general idea of how to scale each spell level. Based on these numbers, I came up with: 9.5 for 1st level spells, 13.5 for 2nd, 20.5 for 3rd, 22.5 for 4th and 31.5 for 5th. I rounded number to the nearest half for this. For example, fifth level spells actually came out to 31.666667. 31.5 was just cleaner.
This lead me to create a second table. In this table, I tested the interaction of the spell slot progression and the estimated damage potential of each spell level. To make this happen, I assumed a 20 round adventuring day. Here's the breakdown:
The wizard came out consistently lower than the fighter in single target DPR using this model. Now, the wizard could come out significantly ahead in the area of effect (AoE) DPR; however, that is part of my premise. As long as WotC uses the estimated DPR and keeps the spell levels relatively in check (as I did here), their proposed changes could work. Only time will tell if they actually do the math though.
Now there are other issues that involve the wizard and the wizard's utility spells; however, that is a different issue.
EDIT: I'm adding my proposal along with suggested damage die here:
