1. I see it as a new type of DPS, as Magic Melee DPS are not in the game, Red Mage is not it. Magic Melee DPS does use Weaponspells, they differ from spell or weaponskill because they can be used close range instantly and also long range, but with cast time.
2. Their Limit Break must be different from Ranged, Melee and Caster. I don't think it's broken, it's basicaly 7s of 100% slow + 4500 single damage + 1400 AoE + 0 to 2000 depending of the Aether absorbed from the party. It gives a MAX total of 7900p single target in comparison to Melee Limit Break, which is 9000p without any effort. It gives a 3400p AoE in comparison to Caster, which is 5400 without any effort. Melee and caster still shines for max damage, while the Source Blader Limit Break is more for survivability. It also has oposite effect of reviving all party member at the cost of yours life if no one uses any action while the Limit Break is performed (7s), most likely when everyone else is dead, while having the down side of the sacrifice. It's just a cool thing, since everyone learns the fight, no one will die anymore. It's just versatile, and in no any way better than other ones.
The main purpose of this is to incentive new systems. Even if there is no new system it's very easily convertible to the actual system. Let's say that I must chose a DPS role, it is Caster, 5400p Limit break, problem solved.
Sometimes is good to have fun thinking out of the cage.
@ About your Edit:
"How can a player destroy it to resurrect themselves" It's a game, and they pretty much can add anything to it. The same thing as when someone gets a ress, they chose to be ressurected. Everyone who is dead near the crystal will receive a unique type of ress buff, and the first one to accept will destroy the crystal, and no one can ress again.
"You are basically shooting yourself in the foot" The main purpose of the Aetheryte Crystal is to ress players, as it costs the same as a ress Spell, and also depletes your MP over time. So you will not want to extend it's life. At Lv 50 you have Reunion, which it basically a "Creckpoint" to all yours stats, you will want to summon the Crystal, burn your resourses really fast, and use Runion. If someone dies and uses your Crystal to be revived, that's a bad team organization.
"Also you need to be more specific with your use of the term Timeless Effect", Timeless Effect is literaly just a resource. Astrologian uses Cards, Source Blader uses Timeless Effects. Every Effect is different, some are DoT, some are damage, some are AoE, some are AoE + MP recover.
"Now I just noticed 3 skills that all appear to be some kind of Tank Stance" It's a sketch, if the devs wants to go the WoW did with the multirole classes. These stances are not implemented in the design, they are just there for potential development.
"Numerology" This same is from FFXII, I wanted to make a tribute to it. It doubles the potency every tick. 21s is 7 ticks, which is 254p. 21s + 7s from Unending Torment = 28s, which is 9 ticks and 1024p. It can't be any second more, or any tick more, because it would double the potency again and become 2048. This 1024p can be buffed with the trait of Mage Blade to become 160% more, total 2662p. This seems much, but Unending Torment has a really high cooldown, so it can't happen often.
"Reunion" Well, they can just enable Reunion to be usable while KO'ed, they can do that.
"Aetherial Gate" I feel that it's needed, because this Job is A LOT mobile, and the Aetherial Gate will help very much to use the skills Retrieve, Charged Retrieve, Faint, Space Control... It youre bad positioned, then it's no damage. It can work in this game as a intant teleport, same as the Samurai PvP skill. And the thing outside the intance is just a cool unique skill for the Job same as the Bard capable to play songs. But the instanced version is a must.
"Ceruleum Embuement combo off of itself" Every combo weaponskill has the combo highlight for 10s or so. If the players used Ceruleum Embuement too early then it will use the combo and get penalized for using such a unstable resource too early and will receive Dbuff. With Deny you can throw it to the enemy, opening for a whole mechanic.
Well, it's a super complex Job, as I said, it is over filled with mechanics and complexity on purpose, so that SquareEnix can choose what is good and what is not good.
I could write about this Job a lot with all the possible combos for damage.