Ahahaha, or perhaps not, I just thought I saw you on Reddit. If or if not, I am glad you wrote this. Because I wanna agree with you!
But I also want to add something else to the mix...
First of all, I agree with you in many aspects. Once the Lyceum days are over, we also don't really have any measurement any more as Merlin and Cyran go vastly different ways. You could say that Cyran was always the second most promising student, but that's just a memory and hardly currently applicable.
We also don't really know the real competition out there. Merlin is at the top, as far as we know (until another cool strong mage shows up, be it on our side or in the enemy team), but after that? Cyran's one of many and his position as Chief Court Mage doesn't necessary mean anything in raw power. And even if it did, just like raw power doesn't mean anything when playing AFKJ, tactics and investment in the right units is also important. And as you have pointed out, Cyran's investment is maybe not in the right places, and his raw power has been bought. xD
What a fun comparison. LOL
Anyway, what I still want to throw in as a counter-argument. Or at least as an argument for "the final battle should have been a bit more difficult for Merlin".
What WERE Cyran's duties? That is definitely up to one's imagination, because we don't really have any info on Court Mage duties. While I largely think that he is more manager than active practitioner now as Chief, HE STILL is a Court Mage and they do not exist just to look pretty.
One aspect they should do is security measures. That means shields of all sorts. And they should constantly work on improving and innovating those shields, because naturally people (as in normal other mages) will try to break them. Not much running around needed here, just plain study work, speed and proficiency in applying them. Cyran brought that quality from school and I doubt he was gonna be content with being "just an average" Court Mage. His imitated shield on the Central Plaza was just for show and "divine appearance". Even as Chief, I think he can't afford to NOT be involved in constant practice and given how he accompanied Orion, I think he is expected to be able to adequately protect the Royal Family directly. (Which makes it so goddamn stupid that he struggled to overtake Gwendolyn's shield who likely REALLY is less trained as a mage.)
On that note, I also think that Cyran DID fight in the war. He was still a regular Court Mage at that time, perhaps already one his superiors really liked due to his diligence. The war took surely some time, and if the King himself went out to fight, then he would take Court Mages with him for protection, as well as employ Court Mages all around the Empire to hold lines. I feel like, as much as Cyran would despise the battle field and the dirty tents etc, Cyran would not "want" to look like a coward and hide, especially when his brother is also on the battlefield. And we sing praises to our soldiers, how would Cyran "want" to miss that glory? At least not unless he had a valid and official excuse. While it's possible he stayed behind in the palace on official orders, I just prefer to think he was pulled into action. And that is again, mostly protection (also against weather conditions), providing lights, hiding presences, perhaps buffing allies etc.
That presence will have given him a VERY good idea on how to structure battles and manage your powers. He was not the only Court Mage to survive, but incidentally a very much liked one, and again I prefer to think he was selected not just for his family name but also his qualities shown.
While this may not be able to outshine Merlin's constant battle experience, I don't think Court Mages (and Army) rest in times of peace. I imagine there are enough "battle drills" to give every Court Mage a reminder of what they would need to be able to do.
I also want to mention the general skill level of these Court Mages. This isn't fully clear, I think, but it seems established that Hypofiends and Hypogeans cannot be beaten with regular weapons or their wounds healed with regular magic. And yet we have two Divine Wars where normal people held their lines against the Hypogean forces. It may have been the Celestials and Dura herself to seal the Hypogeans (and thus perhaps reduce and drive back the Hypofiends as well) but we can't ignore that the soldiers of the Empire, supported by the Court Mages, managed to hold out against all these Hypofiends. The magic of the Court Mages, and other available mages drafted into the war, as well as that of their brothers at the church wielding the magic of the Divine Light, had enough power to stand put. That doesn't mean these guys should be strong enough to be a challenge for Merlin, but I feel like it paints an image of their power scaling and given how I think Cyran was part of the war, it puts him into somewhere closer to the top than at the bottom.
What I also want to discuss is HOW mages fight and apply magic in the first place. That depends greatly on the way magic works in this universe. I may be ignoring canon here, but I just ... dislike something along the lines of "just feel it and if you want it strong enough and you have the magical talent for it - it will happen". The Gala scene, for example, was terrible in that regard. T_T
I much prefer magic to have rules and languages, and you can't just feel like speaking French and then speak it perfectly without any prior knowledge.
So the thing is, that mages will have their favorite spells and can apply them quickly. And given how every mage will have a different repertoire, it's just a matter of having the right defense spell on hand, or being quick and confident enough to cast the spell needed.
I grant that Merlin has a larger repertoire of suitable spells for battle (then again, they mostly use shields and orbs of light to throw at the enemy), but I also don't think Cyran's are that insignificant (given his battle skills in-game).
I don't think he should have had a fighting chance. He did not. :/ But the big deal is the lack of weakness on Merlin's side and THAT bothers me. A lot. Cyran is not a weak opponent. But without Merlin struggling at least once by having to loose balance or have a shield broken, or get a tiny scrape... then I don't know what is at risk in the first place. It is boring to know that Merlin is SO overpowered that literally nothing is gonna be a struggle to them.
Merlin made so many mistakes in previous season or has shown a weak side... in this season, though? I just wanted Merlin to have more struggles than just showing us a sad face after Cyran's gone. And perhaps there will be some more that will balance the fight in hindsight.
Eh, anyway, thanks for humoring me. I have a feeling this is more anti-Merlin than anything but... that really just bugged me. T_T Can't Cyran be at least so competent that Merlin struggles more than just with a sad face? Gah.