So for the most part you will feel bad about taking C2/C3 in a class. The exceptions are when the class has a super scaling attribute or skill offered in C2 like Swift Step’s. It’s pretty simple to see why in almost all cases it’s better to go to a new class than go for second circle.
Let’s talk about short term first. In the short term level 10 skills are roughly equivalent to level 5 skills of the next rank. This is bad. It’s pretty easy to understand why this is bad. You can either have 3 level 10 skills, or 3 level 5 skills that are equal to those level 10 skills + another 3 level 5 skills that are a bit worse but you have cooldowns and more variety to fit into more situations. Level 10 skills should be definitively more powerful than level 5 skills offered from the next rank (both new classes and the circle).
Because you’re forcing yourself to have less variety and less things to do between cooldowns your skills need to be stronger to compensate. But now let’s think about 2 ranks ahead. With the linear scaling unless your skill gets more hits from leveling up (See: muiltishot, fireball) a level 15 skill will be weaker than a level 5 skill two ranks above or a level 10 skill one rank above. This isn’t okay. The level 15 skills need to be stronger than those or they’re throwaways.
The result is that you don’t want to go c2/c3 because they don’t offer as many new skills (often only one or two), and those new skills are typically similar to the ones you already have.
Now let’s talk about long term: Damage skills typically become invalidated as you advance to higher classes. Ones with no cooldown are preferably left at rank 1 for minimal SP cost since the majority of their damage comes from your physical attack later on. Percent bonus skills are the true longterm goals here, and these are what really entice you into going C2. Multihit skills scale alright, but if they don’t gain hits from levels there’s no reason to keep going into the class and leveling them up.
So there’s two ways to make you want to go C2/C3 typically. 1. Lock percent scaling skills/buffs behind these. 2. Have skills that get more hits as they level up. Not all classes have these, nor should they. You can change the balance around to entice people into C2/C3 without either of these. Idea 1 usually feels bad because it’s often not until multiple ranks later that you’re feeling the benefit of this and until you do you feel extremely gimped. Idea 2 is alright, but it’s boring that every decent scaling skill is like this.
While I don’t expect a serious overhaul of the stats and changing skills to use varying ratios to make scaling feel much better even though I’d like it I do hope you’ll take note of this. I think this is very important.