Just adding my 2cents. I've have been raiding for a long time, I think it was back in 2005. What Rhaggy says is so unbelievably true. Patience is key.
It's a hard job to be raidleader. Bring a group together is the 1st hurdle they have to conquor. You think, fine brng 10 people together.. easy. That's only the surface. This is an insight to what a raidleader has to think about.
1st - Tanks. I need a main tank. Ideally, he has to be the right spec and have the right equipment that will let him face a boss and not die in 2 hits. I need an off-tank to handle the mobs that can't be controlled. 2 slots gone.
2nd - Healers. Ideally I want 3. I want a mix of types and healing styles.. I get to choose from priest, paladin, shaman and drood. Priest are versatile and can MT heal, group heal, HoT and shackle. Shamans are awesome raid healers with chain heal, they drop totems to buff the part and can MT heal with their armour buff from crits. Paladins brings buffs to everyone in group and has auras and are never oom for MT healing. Droods bring HoTs aplenty, imba buff and versitility to do other roles if needed. Who do I pick... who's available?
He's only looked at tanks and healers and already, he has an idea when a raid is possible or not. If you make parties for instances you know how hard it is to get these two party members. Very few ppl like to heal or tank. Everyone likes to dps. Tanking and healing are the 2 most important roles. He can't just bring any green geared person, cos it'll be a waste of time for everyone and will be bad for morale.
next is dps... who do u pick? U want a mix because different bosses are suited for different dps. Aran is weak versus melee. Maiden is weak versus range dps. Who do u pick? Obviously, he's going to go for the better equipped people. He's also going to prefer some classes over another because of additional skills that they bring to the raid. E.g. lock or shadowpriest? Hmm... going for moroes.. so SP it is. Going for aran, I want banishers.
point is, even tho raids are planned and 20 ppl might be online. Doesn't mean a raid can go ahead because of these many factors. Now we have 2 raid groups, some ppl might already be saved to one instance and can't go raid with the other.
If you don't raid, you can always go and improve your gear. grp 1 doesn't raid every day, but they don't moan. They just do other stuff like pvp or as I'm doing, improving my gear in instances and quests. There's always room for improvement. If people gear up, the instance becomes easier and many of those factors will go. I've been raiding kara on my priest and drood for months now. I have only just got my 1st t4. Keep improving and it'll slowly happen
Essay over.
Raz