I try and help out guild members from time to time but sometimes I don't feel like helping anyone and I just want to relax and level an alt or not worry about anybody else's problems. Fortunately enough though most of my guildies seem to have no problem with this as I've never gotten a complaint about how I'm not helping them gear up.
In my eyes, they should be working to gear themselves up and if I offer to help them they should be grateful, but they shouldn't expect it all the time. I guess since I don't expect other people's help I think that they shouldn't expect mine. Though I guess never having to look for a tank makes it a bit easier
Also regarding joint guild raids - I would have to agree with Nuberino. Our guild currently is running Gruul's and Mag with another guild that has the other half of progression minded players that we lack. Things have worked wonderfully so far and we'll be starting SSC soon.