The early abilities all seem good enough for strong multiclasses, the strength of the high level abilities seems to vary a bit. Ranger for example doesn't seem to get anything too interesting (Twinned Shot seems cool but costs 3 of your resource so it isn't that impressive I'd say). I was quite surprised by the Druid abilities though, a single class will have access to the Frenzy Wildstrike [Element] abilities as well as strong summons and revives.
Wizards that do not intend to wade into melee will generally be better as a single class as well, there's some pretty damn strong high level spells. I'm slightly curious about Citzal's Armoury (if that was the name), I wonder if it will allow single class melee Wizards to stand up to multiclass melee Wizards.
Overall there is some interesting stuff at the higher levels for most classes, I'm pretty happy with it.