I'm personally a fan of Archivist. It seems many people dismiss is for reasons like it having a 99 turn cooldown on what is pretty much the strongest heal in the game, which normally I'd agree with. (People also seem to do this with SWoT too, of course)
But both of these classes, Archivist moreso, is largely managing these cooldowns. It doesn't actually have 99 turns of cooldown on the heal, since you decrease it greatly with Kathool and the Ultimate Orb, both of which should be used pretty much whenever it's possible.
As far as dealing with regular quests go, Archivist does struggle there, but you can sort of get around this using Trinkets (Which, for the record, are also affected by Ultimate Orb, leading to some potential combos. Unfortunately, the only multi trinket is a Seasonal DC one.
I do think the class has some real flaws though. The stun skill is too unreliable. It works on chance (what even IS the chance?) for a 1 turn stun. Now, that'd be fine, but since you can't stack that, it loses a lot of value when combined with Ultimate Orb, and you'll probably want to do other things like set-up the next Ultimate Orb instead of taking time to use the stun in between them. Maybe it would work better if it had a chance to stun for 2 or 3 turns, but it only works once per enemy per usage? This would make the skill less of a waste on Ultimate Orb combos.
The DoT is barely ever useful. It just deals too little damage to really be worth it. It'd be cool if the DoT could stack, so the earlier you start attacking the enemy with it active, the beefier DoT you can stack on them.
As far as the final skill goes, Archivist would really appreciate a traditional shield. It's not exactly the most interesting option, and I guess not very likely either, if it's going to be based on the Caitiff Saga. I guess we could have Dove's belly-shield for that? Failing that, having a skill that gives you one turn of massive Boost would be pretty fun. On most classes, a single turn of Boost isn't that big of a deal, but combining it with Ultimate Orb can lead to some good results, which is why I think it should be exactly only 1 turn: To play off on the style of the class itself. You can already kinda see this with something like the Mirror Eye trinket. It's 5 turns, yeah, but thanks to Ultimate Orb, you can very easily have a 25% Boost on all your attacks. Alternatively, if you have it, DragonFable Friends gives you 100% Boost for 1 turn. Combining that with Ultimate Orb gives you a full 5-6 turns of double damage.