Should group content offer better rewards (ie. gear) than solo content? If so, how much better? If gear earned in group play should be better than what same level solo content has to offer, how much better should it be? Slightly better mid-game and way better end-game? Way better all the way through?
The factors as to why end game group loot is so much more powerful then solo;
I'm going to play devils advocate here to illustrate a point for the purpose of fostering discussion.
*How many people does it need to run the raid? You need to gather 25 people that need to clear their schedule and free up time, often this is a big problem for many guild/LS where getting 25 people that have the correct job that you need for an encounter. Also consider the normal flow of people leaving the guild/LS invite new player to replace, making that player welcomed in the LS, and is the player good enough or will he be bad that you need to replace him.
Mostly administrative details that are typically handled by the leader and possibly officers. Not saying it's an unimportant element of enabling end-game content, but I'm not sure if Joe Scrub who just logs in, accepts an invite and shows up should be entitled to a higher quality of gear (and/or more ready access to gear) because he's lucky enough to have a small handful of folks who take on the bulk of the administrative details.
* How hard is it to organize the event, with keeping time, track of members, LS website, maybe dkp,
As above. If you've got a group of 18 people, how many people does it require to keep track of that? 1? 2? 3? Again, the people who just log in and accept invites still haven't done anything noteworthy to "deserve" access to any special reward.
* Are there any time limit on the event, meaning you gather so much people and organize such a huge event and the event is time limited.
* How hard is the event, you need every member to be elite(extremely skilled) players to achieve victory
I would say that should definitely be a factor in helping to determine the quality/quantity of potential rewards.
* Do you have a lockout mechanism that will only let you clear the event only x time / week (Raid Lockout)
I could see that as being used to determine quantity relative to the number of people the content was tuned for, though perhaps not quality.
* How long does the event take, the longer an event is ongoing the more problematic to stage the raid
I think the key thing there is to take into account not only how long the event takes, but why it takes that long. If the content can be done from start to finish in 6 hours by an average group but can be broken down into 1-2 hour segments, I'm not sure that the reward should be tuned on the assumption that people are spending 6 hours at a stretch working towards a successful outcome. Not saying that's what you're saying, just another layer to consider.
* Do you need any prequests or attunements for said event, maybe you need all the 25 people if not more to go through series of other event and quest and mission to even be able to enter certain event/raids.
I think the scope of what you're getting attuned for should be considered. Is it a two hour attunement process that gives you access to hours upon hours of content? If so, then the attunement process itself might play a trivial role in assessing quality/quantity of rewards. I think attunements were initially intended as a means of a gear/skill check. (ie. If you can't complete the attunement process, you've got no chance in **** of being successful in the content you're trying to get attuned for.) On the other hand, is it a 20 hour attunement process that gives you access to 1-2 hours worth of content? If so, then that definitely suggests that if you're successful in that 1-2 hours there should be something glowy and delightful at the end.
* Do you need gear requirement or buff food / consumable for the event
I can see that being a consideration more from the gear requirement standpoint. If you need a certain quality of gear to be successful in a certain part of the content, it wouldn't make sense that you should be rewarded with gear of lesser quality.
* Running a raid also involve to some degree solving drama or problems that might occur
Again, administrative. If the leadership is good and drama crops up often enough to be a nuisance, there are ways to deal with it. If the leadership is poor and drama crops up. find better leaders. I can't say that I think tolerating poor leadership should entitle someone to a particular reward unless the content is tuned such that only a handful of people are able to participate in it.
* Orchestrating 25 man so that they work in harmony and beat said encounter
That's definitely a challenge that extends beyond administration and I think that extending one's consideration beyond not just how to kill the monster in front of them but to how to help the people they're with kill the monster, there should be some additional reward.
* How rare is the item / drop rate / or maybe you need to collect parts of it and build the item over a long period of time. (Aka relics) Add this to that you are competing with at least 25 people or even higher numbers since most guilds/LS have more members then that.
Something of a tuning issue. Well, mostly a tuning issue. If the rewards are tuned in such a way as to make you feel as though you're competing with the people you rely on to be successful in the content, maybe the quantity of rewards could be re-evaluated. If it's simply a case where the rewards take a long time to acquire then yes, I think they should be of a higher quality than something that comes more quickly.
Continuing with the devil's advocate theme to more succinctly illustrate the point of administrative rewards, if I assemble a party for the purpose of developing my character, should my character develop significantly faster than the people I find and invite to the party because I took on the additional task of forming the group? If not, should the entire group develop their characters faster than a solo player because someone else took on the task of assembling the group? Or should the group be able to develop faster than a solo player (through skills and/or gear) entirely based on what they actually accomplish in the group?