100% agree.Solo content has virtually no rewards, I don't know what your talking about. Once you get rank 10 and endless wave 30 there isn't much motivation to do anything else. Having more solo content that rewards titles and mounts will give people something to do whenever they log on.
If I log on during the day, I've got pretty much nothing to do since I don't raid every night and I don't farm or play the AH. Garrisons will go a little way to fix this in WoD but other than that I have no motivation to do anything other than sit in shrine which is a situation I'm not happy with. I'd love to be able to go off and work toward a mount or title but at the moment there are none that I can do. Sure more old mount bosses will be soloable in WoD but that only goes so far.
Also, saying that a multiplayer game shouldn't reward solo play is a pretty ignorant statement because multiplayer means different things to different people. Sure for some multiplayer means accomplishing goals with a group of people but for other multiplayer simply means that other players are playing in the same world as you. I think both of these definitions have a place in WoW and should be rewarded similarly.