Invocations, evocations, spellcasting, yes. These are the marks of the hybrid.
I'unno, maybe it's a stat thing. Pure Int dudes don't really need anything besides int. Pure dex ones have stabbing and stealth, which get borderline broken at higher levels. Pure strength gets... armor, which has only just become non-crap again, and melee/crossbows, neither of which is going to get you through the game without god-aid.
I really doubt anyone here would be disappointed if most everything besides th'spellcasting/invocation/evocation skills recieved some sort of emergent abilities as they reach higher levels. Spellcasters get new abilities (spells), invokers and evokers get new and more reliable ones. Everyone else gets jack. Well, they get better at what they had, but they get nothing new. That's kinda' boring, and inequitable in comparison.
It's not like it's something massively difficult to implement into a RL. I can name at least a half-dozen that does it right off the top of my head (Heng, T4, Steamband, Incursion, Dungeonmans, Caves of Qud) and there's more beside. All we'd really like to see, I'd think, is stuff like mighty blow, maybe a charge attack or short-range pierce or crap, yanno'? Something so we get more than +1 to hit/dam and some speed improvement from getting another level of Axes, while the fire-spitting dude gets to puke fireballs out 'is arse for the same gain.