This is something I've wanted to correct since I first read it... xp gain is not as plain as you see it. XP gain increases every 25 levels from level 1. So at mzzery's level, it's 41 xp per +1 xp gain. For +200 xp gain per hour, it's actually 8,200 xp per hour. As stated above, that's roughly one to two creature kills (depending on Lib)... this is still not to disregard that players, even at my level, need to deck themselves out with all kinds of potions and buffs ON TOP of the relic bonuses JUST to hunt successfully.
When, and if, I finish reading this (now) 39 page thread... I may or may not leave another reply, we'll see. 
Correct. Depending on level, it does go up, yes.... Every 25 levels adds. I believe I mentioned that the level has an impact (it's +200 xp base per hour), that's not even a creature kill worth of xp a day, even if you don't calc on Lib or AL kicking in.
Since we are discussing numbers...
They have several inactive members (backpacks and M/A, plus 5 others that are currently listed as gone 7+ days, which in effect means they give the guild no xp no matter wether they have upgrades in xp gain, have an xp gain relic, or wear xp gain gear). They have 31 active members. Those 31 have an average level of 209.
If you look at the xp gain mouse over ingame, xp gain is explained like this:
"Note that your 'xp gain' is allocated, plus a bonus of your xp gain times a multiplier equal to your level divided by '25' (rounding down). Note the actual value is always reflected in the quick display at the top bar xp mouseover. Note also at lower levels this value is scaled down up to a reduction factor of 10 to stop it potentially being too overpowering. Below level 25, no additional bonus is applied. "
For me, that's as you said 41. For the average Fracker, it's 33 (our average level is 841 atm).
For the order of the blue rose, it would be 8 for their average member. That's 1600 xp per hour, or if they chose to empower it to 10 (which costs 3,550,000 gold if you are lucky, but usually closer to 10 million, since if you fail one of the 10, it resets back to 0), it would be 3200 xp. That's unless they are in the low levels that decrease it... a level 26 would get 20 per hour, with the 1/10 scaling. A level 25 or below would get nothing.
If you buy the xp gain per hour, you get +25 base per hour for every upgrade, without having to fight another guild for it = 200 per hour for someone with 8 per, as their average active member has. If you then consider that you can upgrade the xp gain 50 times in the upgrades section, you'll know why I said an xp gain relic gives just a drop in the ocean worth.
If you take into account their max stamina average....
They have 9 members with less than 1k max stam, and the average is 2,356. They have 4 members with more than 5000 max stam. It would in my opinion, based on all these facts, be quite a bad idea to make the rest of that guild go sit on a relic, when only 4 people would gain from it, and ONLY if it was a relic with stamina gain on it. Only one of those 4 would gain enough from it for it to be considered useful even if the relic they want would have stam gain on it. Is it really worth forcing an entire guild to walk back and forth every single time they hunt and waste 100s of stamina they could have used hunting, just so one member can gain from it? Not in my opinion.
Of the 31 currently listed as active, 14 have now been overflowing for 321 hours in total, which is an average of about 11 hours per person. 321 x 65 = 20865 stamina. (IF they have no upgrades in stam gain, so base will be calculated, with the structures = 65. If some of them actually do have stam gain upgrades, it's even more than those 20865 stam). Depending on how much stamina you use when you kill a creature, and the average xp you gain from doing it... it's about 1100? creatures that haven't been killed. That's a lot of xp they could have gained right there.
In my humble opinion, a guild like that should focus on getting their members to upgrade their max stamina to prevent overflowing instead, or at least try to make them overflow less.
I know, it's not my place to tell anyone what they should and shouldn't do, and my guild being pinpointed in the thread was the only reason I even looked at it to begin with. I do think it's only fair to try to help point out the facts though, since I do know what a pain it can be to defend a relic. It's a team effort, and as such, something the majority of a guild should be gaining something from that would make it worth that effort. As opposed to what they say in this thread (that low levels quit because they have no relics) I think THAT if anything, would cause people to not wanna play anymore.
(I'm still waiting to see if they will drop their minimum requirement for joining their guild, too, since Zweil claimed the thread was to make it easier for level 25 players to get into a guild... they have their minimum set at lvl 100, and it will soon go up to lvl 200 it says).