If they go for a more stringent DPS requirement, the timeframe involved kind of becomes relevant because different classes will get damage spikes at different points of time. I run a burst class which means my DPS fluctuates quite a bit depending on where in the fight you cut me off. Running an encounter long enough to really even out the burst and sustained runs the risk of resource starvation in a lot of jobs. There's also that some jobs have a much higher overall DPS potential than others, so if the dummies aren't job-specific the skill involved at a job to beat the dummy will vary pretty wildly.
So the question is how stringent these tests are even going to end up being--if the Advanced DPS Dummy just tests to see if you can average out to 1K DPS over the course of a three minute fight, it'll be fairly useless. The ideal would be job-specific things designed around their idea of ideal play of each job, but we'll probably end up with more of a bare minimum competence test that lopsidedly favors some jobs over others.
I'm not sure how relevant it will be, but for perspective I can give details about how Proving Grounds worked in WoW (and this does sound like it will be similar, i did some quick googling but haven't found any other MMO things like them).
You got the exact same requirements for each class, the differences were totally defined by role (and yes, this led to some pretty big discrepancies on each for top completion scores). All three specs had waves of mobs to deal with.
I never tried to tank challenge, but DPS had stationary targets (some had varying effects, but never did actual damage to you) and failing to DPS them down in time meant they'd explode and you'd have to restart. Main things tested were switching to priority targets (usually new adds with less HP) while maintaining DPS on the "main" mob.
For the healers, you got a team of NPC party members (tank and 3 dps) and your job was to keep all of them alive with various CDs, status removals, ect Losing any of them meant a wipe and having to start over. Main things tested were maintaining HPS while managing mana and blowing CDs at the right time (that NPC was so good at holding aggro it was pretty dangerous, he could have 3-4 "boss" type monsters on him at once).
Obviously that all wouldn't apply here, and I would *much* rather job specific challenges turned up a notch, but honestly giving the same challenge to the different classes might be for the best since that's what ends up happening in dungeons/raiding anyway.