So, Erom has finally made it to the giddy heights of level 10 in my rusty man challenge. So far, there hasn't been a fight that Arcane Shot + an angry pig can't handle. It hasn't seemed particularly slow, either.
So why does it all feel so unsatisfying? Well, without the little rewards that come from new pieces of gear, abilities and talents, the game feels pointless. Considering how I've mocked those who play for gear, not challenge, this is deeply hypocritical.
Without the new toys every half hour or so, the incredibly repetitive nature of the content itself becomes more obvious than a naked elf on a mailbox (and Cataclysm levelling is quite good by the standards of the genre). By adding new skills and talents every few levels, this gets disguised - the encounters seem different because we have more buttons to press, even though the mobs themselves are almost identical.
I wonder if that's a clue to bringing some of the interest back to the solo game - make the encounters much more different. If anything, Cataclysm has taken a step in the other direction - for example, fire elementals are no longer immune to fire. Make the poison from scorpions hit like a truck, so that dispelling it is worth the bother; make melee mobs nasty enough for ranged types so that they have to kite, rather than simply spell them in the face. Anything to make different encounters need different tactics.