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The mainline inf is fine as it is, they just need to reduce guards costs and make infantry call-ins back to 1 CP instead of 2.
Guards and Shocks being 2 CP is a fucking joke.
Actually they are not fine!
The fact is that Conscripts are dealing low damage and have the same durability, as far as I remember, no matter whats their veterancy level.
Initially, the 6-man squads helps them remain on the field but late game they are almost a joke as opposing armies have every sort of weapon/upgrade to kill them fast. So, by end game, you have Cons that deal somewhat better damage but can't stay on the field long enough, they lose DPS rapidly (cause of individual models being killed really fast) and, no matter what, they feed enemies veterancy.
Another mistake you do is that in your mind Guards and Shocks are a "replacement" for mainline infantry.
These are call-in, doctrinal infantry units! They aren't stock infantry, they aren't available to everyone and many commanders don't even utilize them. The fact that most people prefer to have a commander that has some sort of call-in infantry, simply confirms that Consscripts alone are lacking to some extend and that, with the lack of dependable late-game tanks, forces Soviet faction to be hooked on certain commanders...