We definitely recruit "casual" (non raiding members). We're really big on playing with people you enjoy being around. Along with that, if the member doesn't necessarily want to raid every week, if we need to fill a spot, we always go to them first instead of outside of the guild. If you would like to chat a bit more about it, feel free to add me on Battletag: Nathan#1453.
Unfortunately at the moment, we would not be able to guarantee a core spot for a tank. We would consider a plate melee dps though. Please let me know if you have any other questions!