Ach, OK. So if it is about encouraging new players, I withdraw my "really does not matter" remark.
I'm sure that how they described it, but ...
they are on maximum level quickly (which is not even rewarding) and have no idea what to do
but are you sure that keeping them alone on lower levels with "no idea what to do" would solve their problems? Is there some magic that allows you to understand your class on level 50 but blocks you from understanding it on level 105? It simply takes time no matter what, but ... on lvl 105 you can get more advice from other players, every run see that your damage increases from 0.00001% of what others do to 0.001% because you've learnt something. And if the gap between you and others is so discouraging, why making the gap bigger would motivate anyone?
This way or the other the trick will be always to find a newbie-friendly guild that can guide you through. Are you sure that it will be easier if new players level up slower? Will there be more people willing to help a lvl 50 player (which will probably mean: run through the instance for them, not teaching them anything) than how many players explain now a lvl 105 new player how to buff others and be useful? If current "you get to lvl 105 fast, but it takes time to gather end-game eq" is so discouraging, how "you get to lvl 105 slowly, and then it will still take time to gather end-game eq" is more attractive?
Maybe it's naïve but I liked the idea that new players get to highest level fast; true, they are useless at first but every little improvement is visible, can then be noticed and appreciated. They still are included in guild activities (even if they just drag along at first). Won't work this way if they are kept artificially separated by a level gap longer. This way or the other new players will be pretty useless to others. The question is which way can they become more gradually useful, and which keeps them disconnected from others (or even a burden for others) longer...
I see one "filtering" benefit: if currently lvl 105 character asks to join your guild, the lvl means nothing. If you make it harder to get to max level it will mean this person made some effort. But it only means the filtering is now done differently (did she start gathering eq? if she gets an advice in a guild run, does she remember it and follow next time? etc.).
There are people who just try and whether the effort comes in leveling or at high level will drop out fast. There are people who in both cases make an effort, because e.g. their friends are playing (still it's weird to punish them to spend more time being useless to peers - it's a multi-player game at the end). But there are also people who would put an effort but need to feel useful, feel to play together with others. For those leveling up fast allows them to be included in guild runs etc. earlier, and is a good thing.
I get that doing hard things feels more rewarding. But, I think, there are less people who are willing to take up the effort. For every case "you analysed" when someone dropped out because it was too easy (really???) there are probably a few where someone tried and stayed because it _was_ easy to be a part of a group, spend time building up eq for end-game (and not useless eq that in 2 weeks could be thrown away), spend time earning gold/dias and investing in the future progress.
(Plus theoretically the game should be possible to play for free. Example: Steps minigame has now lvl 100 mobs independent of player level, right? So this is an example of what new players will not be able to do for longer. And they will be useless to the guild for longer with no guild mats from this mini game... [not true, I remembered this wrong] Just an example, there will be plenty others - you can earn dias on lower levels, but it's easier once you are lvl 105, you can get tp in lower levels, but you get much more per day once lvl 105 etc.)
So 10x to 7x is imo a step in a really wrong direction. But - whatever, fine. I just really hope you don't go further this way.