Well, come to think of it, when that new class system kicked in ,it will effect the skill progression definitely.
Think about your current rank is Rank5 and you change to Swordman C2 in Rank 6.
The new skills you get will absolutely underpowered as sh*t.
There are not much choice for IMC to fix this issue ,but a solution that I think IMC might do is revamp all skill of all class to progress with character level not the static number.
Isn’t that sound interesting? 
I think just reduce a little bit the diference will be better.
Devs know what they are doing xD have more faith on 'em.
I think the important thing about this system is that we have more choices. You’re example also shows that the system may very well not be as broken as some people will make it, you will be sacrificing a Rank 6 class/circle for a Rank 2 class/circle. Choices still have to be made.
And changing the skill progression would be a big deal on the development side, a revamp like you said. Adjusting each class to scale at all the ranks above seems pretty involved and will take more time, and more importantly something they should have done earlier. People have been complaining at how, for example, your base class skills may not be so effective endgame. Your issue has been a concern even in the old system.
I think we already have this topic but that aside that’s what attributes are for. If the skills are 2 weak later on they will probably just increase the caps on there attributes.
No, it’s not ‘underpower as ■■■■’, there’s trade offs for both option.
By sacrificing the skills of a new class, you increases the effectiveness of what you have. the gain on Thrust/Bash isn’t much but the longer duration on Gung Ho and more charges on Concentrate is worth caring a tiny bit.
Also, any attribute investment you’ve made will also gains with the increased level of the skill. Since most attributes require time to train, this means it’ll take time for the high rank class to get its attributes (not to mention higher class’s attribute also cost more at the same level)
Depending on your investment thus far, even low rank skill with good amount of attributes can outdamage the high rank skill for a while. Of course with more investment eventually that high class’s skill can get similar level in attribute as well.
On the flip side, taking new class means more skill you can use, usually with higher power for higher rank class.
And any new buffs you get means one more buff slot taken, pushing you closer to that buff limit.
So tl;dr version:
Upgrading your low rank class - Increases efficiency in what you already have + have invested/cheaper attribute.
Getting new class - more actions to take in order to fully utilize all your skills, which usually is overall increases in SP usage compare to the other option, and having 0 attribute trained means you need time before your class REALLY start rolling. But on the loooong run you have higher potential.
So if it’s a rank without any class you absolutely need or if it’s an alt to unlock certain hidden class then you might consider upgrading your low rank class to cut down on the amount of investment required to reach full potential.
Early tier classes skills aren’t underpowered. In term of dps it’s the same as high tier classes : little cooldown with little damage versus high cooldown with high damage. It results in each skill having the same dps more or less (for example swordman Bash lvl 15 used every 8seconds would do more damage than cataphract doom spike (well before the up of cataphract anyway since it seems most of cataphract skills hit twice now)
What gave the notion that lower tier classes have less damage?
I think people are reading these base numbers off the skill sim/database and choosing skills that have high base damage.
Truth is, most if not all damaging skills have scaling attributes, so they all scale with your stat development. It’s true that something that has a higher base damage will inevitably do more damage, but it’s your choice, the scaling makes it less noticeable depending on the skill.
Skill damage is by no means a static number.
Many skills also get special augmentations through attributes even at lower rank classes (like a stun or knockdown).
They did think this through.
I would suggest that, glad its already being done that way! Just hope the non-damage skills and everything else can scale around stats as well, so each point of stat is valuable.
Stats are a core character mechanic and should require planning ahead, now I’m just hoping that every stats is more or less important to every class.
it’d be good if you could take all the jobs at any level…
No it would not lol. “let me be oracle at rank 2 and grind easily with call of deities”.
That would also require a re balance of attributes and base values on all skills. Seriously we have enough options already.
You should look at all the others threads about the Class System, you may find them interesting or funny 
I think it would help serve to be more compact with your skills. You could grab some more skills and buffs from a new class, but the limited number buffs you can have on you (without the help if a kirvis) may give you incentive to power up what you have, as well as it being annoying when you have 12 attack skills you have to keep track of.
Another thing is, it seems the last 2 ranks of swordsman look more like supportive roles, while the first few seem to lean more towards outright damage or tankyness. Some classes may synergize better together, like barbarian and hoplite. It’s all how you want to build. I’m getting a little tired of people saying “oh lawl, why would you want lower rank classes anyways, they’re always weaker.”
THIS!!!
Because cleric (as a example) has no useful skills right?
Divine might - garbage
safety zone - obviously 2 weak for pvp or pve
Heal - This skill. Only a idiot would take a skill this weak and useless.
But… Heal is useless WHEN YOU HAVE ALCHEMIST POTIONS MAUHAHAHAH jk 
But seriously, the only lower ranked classes I don’t particularly like would be Wiz … at least C2 considering it gives you 1 new skill which doesn’t seem that helpful to me.
Thats fair i think wizard needs a better attack skill its supportive skills like sleep and lethargy are good but they are skills you want later not off the start when you begin leveling. Also from what i have seen magic missile looks decent but that’s a c3 investment,
Also my experience with wizard was rather short so if energy bolt or earthquake are better then i realize feel free to correct me.
Naw both are pretty bad but Earthquake is an amazing disrupt so for PvP (I would probably have to actually test this out later for a better judgement) hitting a cleric in Safety Zone might be worth it if it works. Energy Bolt… maybe with Joint Penalty otherwise other skills from Rank 2 classes and up are way better.
Yea i see a lot of lvl 1 earth quake just for the cc.
It’s all good i think. For a wizard, it will increase the duration of their buff and debuff skills. Having the privilege to go back to your previous class is a good idea. With this, we’ll have the chance to maximize some skills and attributes.of our previous class. Pretty balanced for me.