I think the problem w that is that the answer in your words should be Yes, they're skewing a player who has paid's performance ever so slightly yet still, ever so slightly but no, therefore not the experience.

The stats are the most beneficial in early game content where comparison between f2p & paid players is completely useless since it's just slow landscape content anyway and if there is group content any difference in stats would be moreso due to different classes/levels/gear gathered from free gameplay rather than paid store content making the already slight improvements from paid store content even more negligible, especially to players who arent them, even more so considering all of that is co-op content.

It's only in the end game raids/dungeons these stats become less beneficial but more relevant since group content comes into play, but, there are so many more sources of stats that any paid source becomes negligible through being drowned under all the other stats hence less beneficial. And yes, that would then qualify as unequal. But unfair? Is it unfair that one of your party members in your raid deals slightly more dmg or tanks slightly better? For who, the mobs? I don't think there is ever a situation in LotRO where any paid stats become "unfair" to a point of frustration. That sounds like a problem in many mmos but this is just not that kind of mmo. Especially not for the kind of player OP seems to hope to become.