I agree with Jas D, that sign and not sign is a bunch of BS, personal approval doesn't prove jack, not even that you would like or dislike something if it was added, peoples minds change after the fact all the time.
But I do agree that this is a bogus idea, these modifications are too strong, with some additions that are far more powerful than even the best runes, the energy regen is way more effective than 5 energy or 30 health, and the balance of power would be influenced, only negatively.
If these mods where offered, everyone would pick added energy regeneration, and it would simply make it easier for guild members to cast more, this is a clear alteration of energy management and would certainly change the way people can cast spells, 1 energy regeneration isn't just a point or something, it is exactly 50% more on a warrior and 25% more on a caster, that is a vast amount, you may as well increase your energy pool by 50 percent, or your health by 50%, that is exactly the kind of impact it would have, and having an extra 200 health is ridiculous, just as ridiculous as an extra energy regen.
I wish capes were personally customizable, that way players could choose from even more capes, including much more diverse kinds and styles of capes. Your guild could choose your logo and cape colors, but the just any old cape doesn't look good on any old character, and the normal capes we have look horrible on Assassin and some other characters, personallizing capes is just as big a deal as getting 15k armor, and the only option we have with it is to take it off outside of PvP.
Perhaps if they allowed people to choose their own capes, and perhaps if there were runes for capes which were balanced, and everyone could use seperately, than something like this would be acceptable. But 1 damage reduction on a class who doesn't stress defense, and 1 energy regeneration on anyone, too broad to be useful, or way to powerful. They could try and make some sort of bonus for a Guild in PvP based on a patron God, with the same kind of universal boosts given from their messangers, but the use of this in PvP is a very volitile PvP issue, and the use of it elsewhere is unneccessary and overpowering.
You wanted an explaination, you got it, lets hope the OP can recognize the factors. I believe his intention was to offer a small addition to guild capes, but these arn't small, they are huge and arn't even balanced with eachother, let alone balanced with current gameplay.
There's more to insignia/logos/emblems etc. than just simple appearance. The capes are fine as they are and no need to give them special abilities....
