How are you not dominating with a paladin? Holy retribution is the best cleave in the game and especially for heroic leveling. I was one-shotting mobs in reaper at level 15 with a first-life paladin with full free-to-play limits. The main issue was without tomes, past lifes, reaper points surviving was more the challenge esp with many reapers.
The reason there is a spike around 7 and 15 likely has to do more with bank characters being iconic or vet level II than anything else. I am sure there are many level 1-6 bank characters too.
Level cap should be the focus of balance measurements and adjustments for the simple reason power from past lifes and reaper trees is so ridiculously strong that anyone with wings should cruise through level 12-19 solo on mid skulls fast on EVERY class. If they aren't able to do that they need to learn to play the class better or adjust their build. Showing a screen shot of damage in elite for an accomplished character is sort of meaningless as nobody with wings will even run on that difficulty.
You were successful at getting warlock DPS nerfed at 30 with posts like this showing heroic dps and I think ultimately you were proved wrong that those nerfs were even needed. Sorc had better DPS at the time you called for warlock nerfs even before the adjustments. Warlocks were not over-represented at the time and they are highly under-represented now.
I hope the devs look at more data than something as ridiculous as a winged character at level 15 that likely has at least 15 extra AP which is huge at that level. And they should also reverse some of those warlock nerfs.