It's more like the opposite of what you're thinking right now. I get consistently matched with Crystal players at diamond 5, but I was already matched with Crystal players when I hit Platinum 1. If anything, this was to further close the gap between matchmaking ranks so the disparity of player skill difference is smaller. Don't know how it will affect queue times though.
After reading these patch changes, most jobs are getting really buffed in terms of survival and mitigation prevention. Black Mage in particular got a huge buff - Nightwing now even slows enemies in addition to its sleep effect, the barrier potency increased by 4000, all its finishing spells have increased potency, and its LB also giving 20% mitigation. That might be an issue, considering how fast Black Mage charges Limit Break compared to other jobs. It's a huge threat when left alive, moreso than any other job at the moment. These changes are really overtuned in the hands of a good Black mage.
Summoners got a powerful buff to Radiant Aegis - mitigation went up to 20% and barrier increased by 2000 potency. Casters are pretty tanky at the moment. RDM got nerfed slightly, but it's alright since they can heal or increase their lethality by a crazy amount.
Dancer got some survivability with honing dance offering 20% mitigation, which is nice since Dancers are now the "healing/defensive ranged support" job, Machinist is the high burst damage ranged job, and bard is a mix of the two with decently high sustain DPS. Really good changes all around for these three ranged roles by cementing their identities uniquely.
If anything, these changes is basically a huge stealth nerf to ninjas in the opening phase (has anyone been assassinating Yoshi P lately?). Assassinating someone is goanna be a lot more annoying for me, but I think it should be alright..? Going to have to try it out a bit more to tell though, but it looks like teams with Black Mage will dominate the opposing team unless the opposing team can quickly get rid of the Black Mage.