There are many products in the Super Codlivine range, but if you are referring to the Super Codlivine supplement (which I presume was the original product) it is a broad spectrum vitamin and mineral supplement with added cod liver oil. So no point feeding it with a balancer as that also acts as a broad spectrum vit/min supplement.
Actually feed balancers aren't broad spectrum. They are designed to balance an incomplete ration, for example if you were feeding below the manufacturers recomended rate of Cool Mix you would top up the vuts and mins with a balancer like Gro 'N Win.
Balancers don't contain a complete daily does of vits and mins so maybe you should just feed a supplement like Equivite instead of the balancer - works out cheaper!
"When TopSpec Feed Balancer is fed there is therefore usually no need to add any further supplements, other than salt or electrolytes for sweating horses."
and I'm sure most other balancer manufacturers would claim the same!
But, yes you are right that if you just want to supply vits and mins then a broad spectrum supplement is fine. Balancers are more than that though and usually contain protein, probiotics etc, as well as a full range of vits/mins.