I think one of the biggest mistakes CoH has made is the attempt to satisfy both soloists and groupers. I say this not because I think it's impossible, but that the dual goals cloud each other in more subtle ways than I would have guessed.
One problem is now blindingly obvious: the solo experience is not at all representative of the group one, so while you throw yourself into the game solo to get an understanding of it, you get bored quickly of the monotonous pace. A good group, facing a really hard mission will in fact be required to act quickly and generate far more of the harrowing moments that make a game exciting. It's not at all immediately obvious what the group experience is from the solo, so a lot of soloists come on complaining that the game is dull.
Secondly, and very much related, the fact that you start out solo guides you into a style of play that sucks the fun out of a good group experience. I like playing smart and not dying, but I equally like charging into a battle and letting all the ATs contribute to maximum effect and creating drama with the risk. The alpha strike/tank rush (well, blaster rush in CoH) gameplay style that is predominant here is the result of building a system that is centered on solo play, with group play just being a rampled up version thereof. It's just not very fun.
Anyone who's talking about leveling taking too long is effectively saying that the combat is dull. It's my opinion that on investigation, you'll find the above to be the core reason for this. While CoH has managed to build a combat system that is immediate, easy to get into and fun, supported by an AT system that provides clearly defined roles for players to subscribe to (and bend!) it's not excercised to it's full potential by the enemies and scenarios it's played out in. This unfortunately makes it a short lived thing. The only respite is the gaining of a new power, thus the obsession with leveling.
I'll be interested to see how the game evolves now, but they really need to pick solo or group, or at the very least split the game on those lines and focus on each as it's own concern. They do not lie on a single continuum.
