Scaling of abilities to a player's level is not a step in the right direction.

[Charismatic]

Thing is if they make con for example have more curing/support skills, at the same time reducing their total skills, by about 1/3rd how will they solo? at the same time when cross class skills will be a very limited resource early.

I don't know how much mage soloing you've done but... to solo at a decent clip you don't even need more than a couple of nukes and then support spells.
Put on Scourge and Banish from THM (which will undoubtedly be gained at a low level) and the CON skills should be enough. THM soloing is what I'd be more concerned about depending on what levels they gain certain abilities.

I honestly don't see how this will be a problem for any class in the game other than potentially THM, yet I doubt it'll be a problem for them either.