More so for some role versatility. While a WoW veteran in years played (on and off for the years, but I've been around for many), I grow bored often, do not reach 80 and end up letting my sub expire.
For all the time I've played WoW the only hybrid character I played to 80 was the paladin. I got a hunter to 80 and a Warrior to 50 something. I had a rogue at around 40 odds, but got bored. I really am a casual player who prefers to have fun, explore the world, and basically find ways not to get bored. I always think the hybrid classes scream at me for this, but I'm an alliance lover and playing the Druid as a Worgen was awful. Hate worgen animations. I find it hard to play as the older models due to how bad they look/animate. The levelling process is actually something I enjoy, so I always thought going a Death Knight would be against my 'character philosophy'
Some of the more gimmicky changes to MoP such as pet battles, and then obviously the whole new race and class seemed fresh and peaked my interest enough to sub again for a while. I do not care about popularity of classes, who is best vs who is the underdog, simply what I find fun. Your suggestion seems to bluntly suggest the rogue will wipe the floor with the monk on DPS, but as I said above I wouldn't really care as long as my choice didn't bore me.