Best way I could see to fix this would be to cut folerit's re-spawn in time in half.
Yes, he could be more easily farmed out.. but due to his difficulty, not many people are going to do this unless he is the only thing available. The result would be a much higher probability of him being up should you wish to progress in the teir. This would still allow guilds who can't beat the wing in one night, the ability to go back in a timely manner without having to kill him again. It will also still allow other guilds to make use of folerit clears should another guild kill folerit, but only if they do it in a timely manner.
I would like to note here that if a guild can kill folerit they should be able to (assuming nobody leaves the raid and they have time) fairly reliably kill all the bosses up to farhanieth. At arrival to farhanieth, they will once again be challenged with a near comparably difficult encounter to folerit. This general result here, should be that guilds who beat folerit, will also clear all bosses up to at least farhanieth.
Is this fair to the guilds who have been "able to take advantage" pre-change? No, but fairness has never been a concern of making things "right" or the intended difficulty from a developer standpoint from what i've seen.
I would also like to note that folerit is one of the first "hard" mobs. In other words, he is one of the first mobs that few guilds have shown the ability to beat in a consistent manner. This is due to higher tier encounters more so requiring both gear and a higher level of raid wide competence. Relevance of this is subject to interpretation.