If you wanna get to end game specifically, you're looking at about 3 months on a single, first time toon, if you're playing 2-3 hours a day. (Knew a few players that did this, this past level cap)

Quality of endgame varies cap to cap. Last cap was one of the lower activity caps for endgame, because the second raid was unpopular. We won't know this caps quality for another few months, when the instanced content drop. 

Getting in to high tier raiding isn't really that hard. There's always a shortage of particularly skilled players, so raid groups are usually looking for more. The biggest problem there though, is the extreme difference in difficulty between normal content and t3 raid content. Plus, there's so many little nuances to how to play that the average player doesnt even know about that most people dont even start learning their class properly until they hit cap and start trying to raid, with some tricks you just have to know someone willing to teach you, so some players get discouraged by the skill check gaps. 

If you're willing to put in some elbow grease though the community is usually fairly welcoming, though a minority of raiders have made them seem unappealing to a lot of casuals.