From what I read on the UK forums and the numbers I crunched when the information was made available, there are some characteristics of guilds that have some people doing better or worse with the new system. If the guild in question is generally made of active players and completed the guild quests daily (more or less), then the same level of quest completion gives a bit more guild coins to the player that completes regularly. If there was an imbalance of inactive players, there is a drop in the reward.
Since all levels of the guild now get the same guild coins for overall completion, I am using the highest level tier for comparison. For the largest guild tier, 99 people, there needs to be a completion of 44 people to get the equivalent reward; on the low end of 56 members, the completion level is 34 people. Here is the table I worked out for overall comparison:
total #_____new reward_____old reward______% to obtain________# to obtain
10____________75_____________70_____________93%___ ____________9
20___________115_____________70_____________63%___ ___________12
21___________118_____________77_____________65%___ ___________14
35___________153_____________77_____________50%___ ___________18
36___________155_____________91_____________59%___ ___________21
55___________193_____________91_____________47%___ ___________26
56___________194____________119_____________61%___ ___________34
99___________263____________119_____________45%___ ___________45
There is a discontinuity at the transition for each stage in the previous group, so the guilds near the bottom of the tier need proportionally more people to complete the quest. However, this can also be looked at as the guilds near the top of the tier were previously getting penalized. Given that the completion rate before was 80%, there has been a significant drop in the completion rate for the same return.
There really are two separate issues, the new system of reward and the quest requirements. They are difficult to separate, because the quest requirements directly affect the completion rate. The new system does favor active player groups and does seem to penalize the guilds under 15 members compared to the old system. It removed some fairness issues, as some guilds have taken advantage of the inactive/active discrepancy to gain more coins.
As for the quest requirements, I will just repeat mu previous position. It should have been expected that the overall difficulty of the quests for players over level 50 increase once quests were made for them. What should not have increased is the relative difficulty of the quests. There also needs to be some decision made about where to set the playing requirements for people to reasonably complete the quests, and make sure that the new ones are in line with the older ones. And since the amount of coins returned has gone up, players who completed every day before will have to look at what they actually need to do to get the same amount of guild coins. Unfortunately, that number will change based on several guild characteristics.

