Actually, En, I'm not sure that he is agreeing with you at all. The words are in italics, which sometimes means that someone is not telling the truth. I thought you should know, since I am so often confused by this very practice.
In this case, it seems very likely that TJ is not actually agreeing with you, because it is difficult to tell whether moves look "unpracticed" or "unpolished" in a comic book. The issue is open to interpretation even more than is the film-material, since only snapshots of action can be shown. Outside information becomes much more important in these cases.
Some outside information about Sidious during the time period in question includes:
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[*]He no longer needs to hide his Sith Identity through the Force from the Jedi
[*]He can no longer predict to fight a lightsaber-wielding foe, as most of them have been killed
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From these data we can draw some conclusions. Some of the conclusions we could draw include:
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[*]Sidious is now free to maintain his martial combat abilities.
[*]Sidious no longer has a motive to maintain his martial combat abilities.
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It is likely then, that Sidious is is much the same position that he was at during the events of Star Wars Episode Three: Revenge of the Sith; he will continue to be a particularly deadly swordsman, especially when his immense Force Mastery is brought to bear. This can be seen on film; Sidious remains deadly after decades without practice. There is no reason for this to have changed, even though the number of years has increased. However, his technical skill is not likely to have improved. There is no reason for him to continue maintenance on that ability. (I remember one characterization, perhaps by Blank101, that included an active disdain for the weapon as a tool of his now-defeated enemy.)
None of this, however, is enough to conclude that Darth Sidious will be in a weaker position during this fight with Mace Windu than during the aforementioned film. During the fight in the Chancellor's office against Windu, Sidious had the disadvantage of decades away from the blade. This will not have changed substantially, so no decline can be found through this factor. During that fight, Sidious also had to deal with a superior number of combatants. Indeed, the time he took dispatching those other three Masters (scant though it may have been) allowed Windu to "sink into Vaapad" (Ep. III Novelization) and put the Jedi Master in a position to win the battle. Sidious will not have distractions in this fight.
There are other ways in which the DE incarnation of Sidious is actually in a stronger position than his former self. He is no longer burdened with an aging body; vim and vigor have both been restored by way of the clone's youth. This may be incredibly important (or not) depending on how the "superconducting loop" is evaluated. If, as you yourself agreed (several years ago) it only allows Windu to match Sidious' Force Buffs then the physical restoration becomes very important indeed: as Sidious uses less power to become physically able to fight, Mace's unique metaphysical gifts will help him less.
What we are left with, then, is an Emperor restored to the exuberance of youth and freed of the obligation to call on the Force to endure a fight. Though his technical abilities may not have improved, they will not have diminished much since their last usage. These two factors combine to deny Windu his most important advantage: Vaapad's metaphysical superconducting loop. An Emperor with more advantages and fewer disadvantages cannot help but to win this.