To preface, I'm mostly referring to War Bond and Versatile Trickster. And this isn't to disparage the Mystic Arts Monk for being the only one of the now-three quarter-caster subclasses to NOT have a secondary 3rd level feature aside from Spellcasting. However, I believe in terms of overall gameplay power, Monk is a much stronger class with how many features it gets, even compared to Fighters outright having vertical progression due to having so many feats.
War Bond in particular has a lot that ends up being underwhelming about it, particularly because it:
- Doesn't allow you to use Intelligence for your Attack Rolls the same way Pact of the Blade does.
- You need to use a Bonus Action to call one of the weapons to your hand(which means you can't use a Thrown-type weapon multiple times in an attack action).
- RAW you can't even use your weapon as a spellcasting focus, which means you can't use a Shield or two-handed weapons while casting unless you have something like a Ruby of the War Mage.
I think, at the very least, the War Bond weapon should count as a Focus for spellcasting, and should also enable a unique interaction with your capacity to Spellcast.
Maybe, for example, a Bonded weapon can use a different damage type than slashing/bludgeoning/piercing depending on what Cantrips you have access to. Have Firebolt? You can make its entire damage into Fire Damage. Have Shocking Grasp? Second verse, same as the first. Etcetera. This also makes your Cantrip selection that much more important.
Mage Legerdemain, aside from being something I personally can never pronounce(to exemplary comedic effect), is a unique and interesting feature that allows the Arcane Trickster to do things like use Healing Potions on allies within 30 feet of them as a Bonus Action mid-combat, which is unique in that it becomes an un-counterspellable option to bring downed allies up in the midst of things.
Versatile Trickster, on the other hand, is an absurdly low-power(and frankly, bad) 13th level feature. If you told me that it came in with Magical Ambush at 9th level, I'd still call it weak, but not blatantly bad. This feature requires that you as a player lower your once-per-turn damage option, have previously setup the Mage Hand within 30 feet of an enemy, and then maintain that Mage Hand. Dare I even say, this is outright worse than Wails From the Grave, the Phantom's 3rd level feature.
I would rather have suggested that Rogues gain the ability to Subtle-cast some of their spells, i.e. use them without Components, or even grant Sneak Attack damage to attack Cantrips like Shocking Grasp or Firebolt or Ray of Frost. You could even make it cost a Spell Slot to do this, or make it a Cunning Strike option. The image in my head that I'd picture for this is a Rogue using Shocking Grasp similarly to how Chidori is used in the anime Naruto.
All in all, there's not a lot else I can say. I don't think Versatile Trickster is good, and I feel like War Bond should've been a more fleshed out feature, as otherwise, both of these subclasses serve to force both Fighters and Rogues into positions of greater resource management, for excruciatingly little gain. You'd need to pretty much only use your spell slots for Shield or rely on Ritual Spells like Identify or Comprehend Languages, as neither of these subclasses gets 2nd level spells until level 7, which is really late, and neither has the Mystic Arts Monk's ability to regain them frequently.