Tony Vargas
Legend
At that rate, we could expect a combat to last about 3 rounds. At 10th level, with casters having 15 spells to spread over 6-8 encounters, that's about 2 spells per encounter. So two casting, one cantrip. The cantrip's one round of half damage would have to make up for both rounds of casting, which'd mean each spell could only do, on average, 25% more than the 'full attack' (let's call it) of the melee types. If we assume the casters are supposed to get equal DPR from the back while the melee types suck it up in the front to dish out theirs. I'm pretty sure spells do better than that.So yeah, the melee types are hitting for more than twice as much damage and can do about 39% to 46% of monster hit points per round (if they hit). Casters with cantrips, about 15% to 20% (if they hit).
Assume the lower half of the caster's spells are consumed on utility or the like, leaving them with 1 spell/encounter, and that spell would have to be about double the damage potential of the melee type - again, to equal the DPR of the melee type who sucks it up in melee while the caster hangs out in the back, and who is shown up out of combat by the caster devoting all his lower-level spells to utility. So, really, it should come in lower.
I have a feeling this math has all been done during the closed playtest and that what they came up with was, indeed, 6-8 medium-hard encounters. Tough and/or boring as that may sound.