I'm really liking the idea of this mod but there are some balance issues to be concerned about regarding some classes anyway.
To start, I think you should decide upon a max level, and scale your exp for a standard terraria playthrough on vanilla so that it feels natural. The default EXP rate is very slow for the leveling process. If you can decide on a max level, you can better tune your bonuses and how they'll play out during a standard playthrough. You can then let players modify their max level caps on their own based on mods that have post Moon Lord content (like Calamity Mod for example).
There should then be more passive abilities to support your classes. Your opener attacks for your Thief class and Heal/Damage auras are a nice start, but try to figure something unique to give to your classes, particularly at certain level caps. If you left your base level cap be at 100, you could set something nice at lower level (1 or 10), and then something at a second big bonus at a later level, such at level 50.
Your archer classes are devoid of any creativity right now and are simply the same bonuses together. A few ideas you could try:
Marksman: Pure Ranged damage class. Adds move speed, ranged damage, crit, and ammo reduction like your current ranged classes.
Trapper: Mixed Ranged Damage + Sentry class. Allows you to summon additional sentries as you level (akin to the Dungeon Defenders equipment). Ranged/Sentry Damage as you level.
Sniper: Sacrifice weapon use speed for high power. Decreased Fire Rate by a large amount. Increase Damage, Velocity, Crit Rate, and Crit Damage. Later levels can grant the Shroomite Armor bonus to the player (where standing still provides stealth but a bonus to damage when shooting while in stealth). Bonus to allow all shots to Pierce regardless of weapon/arrow/bullet choice, if that's a possibility.
Your support class is a bit overpowered. The healing is incredible, but even more so is the damage output of the aura. I think the issue might be more with its range being screenwide, dealing huge damage from a safe distance to all targets. Perhaps requiring line of sight (like how Spears wont hit through walls) or by dividing the damage between the number of enemies affected (so full damage on a single entity, or reduced to 25% when there are a lot of targets). Worms and other segmented monsters get demolished by this effect, but its a good start. This healing and damage outperforms the Tank class as Tanking in my opinion as the armor gains are sufficient enough to reduce damage compared to just healing it back by not getting hit (and not getting hit is standard in terraria).
I do like auras that benefit others for the support class. Perhaps consider an Alchemist Support class. Their perks could involve increasing the duration of Potions, allowing allied units to also receive the effects of potions you drink (including stat/buff potions or healing potions), reducing Potion Sickness time for themselves, and as an offensive ability unique to them: naturally adding effects like On Fire, Chilled, and Broken Armor to their attacks, where higher levels add Poison, Cursed Inferno, and Electrify (as if using Alchemy to coat weapons that do these sorts of effects). Broken Armor and Chilled offer good support while the rest supplements an Alchemist's damage as by default might not have any damage modifiers accessible to them (maybe Throwing by a small amount?).
All of your starting classes pale in comparison to the Hybrid class. To be honest, the speed mod is of such great use that it outweighs any of the other bonuses classes like Squire or Archer get. Also, consider having a base line for some stats at level 1 for some classes. For example, Squire could start with 5 armor, 10% melee power and speed, and 20 hp, then gain whatever its scaling bonuses are. You may even consider penalties as well, such as other damage types that aren't melee, though considering most accessories in terraria aren't like that, its probably not necessary.
Consider making a separate set of class tokens; one that's a "Main" job and others that are "Sub" jobs. Having classes split 50/50 while taking two slots doesn't get much out of the stat bonuses, and only the passives for that class (which is nice too I suppose). Consider a Main job that is not reduced in levels, allowing you to wear Sub Job tokens that are split on level (so a main Tank job will continue to get full bonuses at level 100, while a subjob token will reach Level 50 at the same level, or two sub jobs reaching Level 33). Level up perks can be spaced out that ones that you'd want shared between classes (via a subjob) are gained between level 1-50 while ones you'd want only a main class to have be at levels 51-100.
I said a lot here, but that just shows i'm very interested in a more refined version of this. Let your creativity go at it and bring some nice variety. Maybe if I look into how the scripts are made, I'd consider writing my own. For now, I'm still really enjoying this mod while I explore Titanium and Calamity for the first time.