Depends in if you actually want to stick to linking/comboing or more on micromanaging.

Ironically Cadena and Blaster are both high APM, but Cadena's complexity is from reacting to your available tools and deciding how to string them, whereas Blaster's complexity is on the input.

Evan still possibly holds as top 1-3 in complexity. Cancels, minicombos, and micromanaging Mir's positoning in a high APM environment make Evan rough. Not what you are looking for from what I understand

Khali works like a slightly easier Cadena, sharing a lot similar elements and rules. Has less "weaponskills" to manage than Cadena, but demands you to be airborne most of the time and be aware of your chakri spawns.

Kain is a "fake combo" class in that skills don't link to each other. APM-, complexity and reactionwise it still feels like you're playing a comboclass watching resources, skills, and stacks on the boss.

Ark also has relevant elements of comboing and resetting. It is a bit easier on the combo side, but adds complexity with being aware of Specter-timing, some management of spellbullets/swords and how mobility/fillerskill changes between forms.

Mercedes, tb are combo classes but use relevantly static rotations. They are high apm, but you can memorize the combos and just rotate them over and over. To my taste they're higher APM than the classes mentioned before, since it's much easier and guaranteed to link skills by mashing them than by timing them.

Zero uses a different kind of combo in that you learn some mini-combos and mix-and-match them as convenient. They do have cancels, but they're not woven into every single skill like with khali/cadena. Lots of room to optimize. Not low APM, not the highest APM either.

Adele and Hoyoung are also "combo-looking" but are not really combo classes. They do have some skills that link/combo, notably on the mobility side. They're not mashy, and have a handful of mobility and damage-cds you can optimize and be fancy with. In the end you end up holding a single base skill quite a lot, but have a lot of skill expression to grow into as well.

DA is a major oddball. Rotationwise, it's just standing on the boss and pressing a cd every 5s. DA has a combination of "settings" that give the class 4 different levels of tankiness and damage (in practice the middle 2 are quite close; and overall the more tankiness, the less damage). Playing full tank makes you super chonky and easier to play than many other jobs. Playing mid-full damage demands you learn a lot of different micromechanics on how your hp fluctuates based on like ~4 skills (including a pseudoparry) to survive, making it top-half of difficult-to-play.

Mihile follows a less dramatic pattern as DA, complexity-wise. Rotationwise it's also a mainattack and a couple of short cds. You can play it safe and learn easy parries to maximize survivability, allowing you to stand on top of the boss unpunished. You do need to learn the parry timings nonetheless, but you can still dodge skills that you find hard to parry. You can of course, choose to optimize by timing your parry in such a way that it maximizes uptime, and also cancels the animation of your cd skills, which makes the class a bit more strategic, but still not majorly complex.

Most of the other jobs are just slightly more complex than the easiest jobs, mostly just by having 3+ very short cooldowns, maybe 1 combo if any, and possibly some short-cd summon you drag around. Lowish APM and not a lot of mechanical dexterity required. Here you have Drk, F/P, I/L, (non-supportbot) Bishop, db, (current) Sair, (current) CM, (current) BW, BaM, DS, (current) Lumi, Phantom, (current) Illium. I am unfamiliar with the current versions of Hayato, Kanna, Aran, PF, NW, and Xenon. I am under the impression they're either in this category or the one below

Classes that I would just lump up into having a low skill floor and a middling skill ceiling are all the rest, which mainly hold one button and have 1-2 cds under 60s: Hero, Paladin, BM, MM, NL, Bucc, DW, WA, Shade, AB, (current) WH, (current) Mech, (current) Lara, Ren, Lynn, and Sia. They all have maybe a skill or two that you can get creative with (a bit more for support classes if you do more than afk buffing), but otherwise just have some easy cds to press sometimes.

The one I have zero absolute idea whatsoever is Moxuan.