Kane's Wrath had pretty great unit balancing if you knew what you were doing and how to counter units. The campaign in KW was laughable, however. Red Alert 3 is just utter bullstuff and even more focused on "rock-paper-scissors" more than ever. The campaign still blew richard even in coop.
Red alert 3 was one of the CNCs where you couldn't just spam a stuffton of tanks and overrun the enemy base with them. This is entirely possible in CNC 3 & KW 3 and a bunch of other CNCs.
I don't think the balancing is utter bullstuff seeing how you don't have overpowered units or factions. However
in the end it's just opinion based.
Even though the campaign does not become better in COOP you actually get the opportunity to play it with a friend. I don't know another CNC where that was possible without the use of mods.