There is a fairly serious flaw within the mechanics of the game, that hinder one job in particular, and do have an impact on other jobs that share these mechanics as well.

What I of course refer to is the cap mechanics of the various enhancing and enfeebling magic spells. I will focus on three Haste, and Slow I and II in attempt to explain my theory as best as possible.

Before I dive in, I must state this theory is almost exactly the same as the one I posted that seemed to be the basis to the recent healing adjustments, in which the native healing jobs, were able to (through skill point effectiveness) break the caps imposed on them at level 75, to

1) Make separation between a main job and a sub job, and to establish distinction without compromise among mains.

(WHM benefited as much as RDM and SCH, and all 3 saw separation from sub job healing.)

2) to allow for certain jobs to have a stronger big heal without compromising the core mechanics of the content prior to the 75 cap.

(RDM SCH and PLD gained some strength in the top end healing, without impacting WHMs top dog status post 75, 75 and under is effectively unchanged based on the established skill ratings.)

This adjustment theory applies the same 2 principles, how to effectively establish distinction not only between mains but how to define separation from mains to subjobs. Specifically I will be using RDM in my argument because it happens to posses the highest skill value in both Enhancing and Enfeebling. I will be establishing level 75 as the skill point break point where the new mechanics will kick into effect allowing for higher buff/debuff values. Essentially these are the values I will be using.

Enhancing: 256/404
Enfeebling: 276/424
Slow: 29%
Slow II: 37%
Haste: 15%

Enhancing Magic:

The case for Haste.
The reason I opted to choose this value to compare is because it is a must have buff, that is static from level 48, which means it is attainable via /RDM. It allows for an easy comparison to see the valuation of effective skill point mechanics.

Haste can be broken down as such.

.15/256 = .0005 or effectively 1 SP = .05% Haste.

This implies that for every 20 skill points the Effective skill point value is 1%. This is our established scaling value based on level 75 capping.

Haste is 15% until 256 Skill, at which point Haste becomes 15+((Skill-256)/20)

So for level 99 we would see something like this.
15+(404-256)/20 = 22.4%

WHM would come in a little lower, but the real key is that Sub jobs can not hit this skill threshold. This puts enhancing magic back into the hands to the jobs that should be using it, the WHM's the RDM's and the SCH's, because they can just do it better.

By scaling the mechanic in this manner, jobs with high skill point values are rewarded by being able to just cast the spell better. Players with the gear can extend this bonuses higher, giving them effective value for their efforts in acquiring the gear.

Does this follow our 2 principles.
1) It provides clear separation from the values that /RDM, and /WHM providing clear superiority for the main jobs, and does provide small distinctions among the jobs at the top with RDM edging out the others slightly.

2) It does not destroy the content values of content up to level 75, and targets only specific jobs, and is not negative in regards to any of them. Essentially this is a direct buff to jobs with native enhancing magic.

The case for Slow/Slow II

I chose it because I recall the rough values of both slow 1 and slow 2, and want to compare 2 aspects of the enfeebling conundrum. I also selected it because like haste it is a static value that many jobs can hit the cap of fairly easily with similar accuracy.

First I want to explore the MP valuation and relative effectiveness of the Slow to Slow II mechanics. Using a simple 300Base delay

300/60 = 5
300*1.29 = 387/60 = 6.45 seconds

Slow 2:
300*1.37 = 411/60 = 6.85 seconds.

a .4 second difference for 5 merit points.

Secondly I want to observe MP valuation based on current values.
Slow: 29/15 = 1.93
Slow II: 37/45 = .82

Essentially in terms of effect for value Slow 1 is pound for pound the better spell. Why is this relevant. Well since the level cap change more and more jobs are proving to be able to effectively cap slow I, paralyze I, Blind I. These three staple enfeebles are capable of being capped by many jobs, all with similar ability to land them.

What needs to be done to address this is allow the effective value of skill points to play a greater part. Similar to how the value adjustment to enhancing magic worked above. Following again the 2 principles above.

29/276 = .10 effectively 1% per 10 points.
29+(424-276)/10 = 43.8

New Values:
300*1.438/60 = 431.4/60 = 7.19(/6.45 = an 11% increase)
43.8/15 = 2.92%/MP spent.

Slow II
37/276 = .13 or 7.8SP per %
37+(424-276)/7.8 = 55.9

New Values.
300*1.559/60 = 7.79(/6.85 = 13% increase)
55.9/45 = 1.24%/MP spent.

Again by adjusting the valuation of enfeebling skill in this manner it provides a separation from sub job to main class cap levels, and provides distinction among the jobs native to these spells. In addition to this it does not effectively restrict jobs currently capable of performing these duties (such as WHM BLM SCH) as it is an across the board adjustment, nor does it alter the abilities in content 75 and below.

These changes adjust the values for the top end of the game, values that are stagnated based on old level mechanics. Essentially you could say level 99 jobs are playing by level 75 rules. These adjustments are as much needed as the healing adjustment I lobbied for, increase the capabilities of the main jobs that have the tools without negatively impacting those jobs at lower levels, or in sub job roles.

The mechanics of the game are detrimental to the current support system, specifically for RDM which currently offers just as much as a sub job. I think SE should seriously consider adjusting these mechanics, it doesn't make sense to pile a bunch of stuff on a foundation that is wonky.