Theory - Support Items and Non-Supports

These two items, lets face it, are very strong. They are so strong in fact that you can build a support
with just these two items. You could take just about any champion in LOL slap these two items on them and they will have a meaningful impact in teamfights. It is undeniable that these are support items but they are such strong items that you rarely need anything else as a support.
However, are these really the problem for the support role? After all, as a support main I must admit I feel really strong once I get these items and I think that is an important fact. There are so few people that want to play support that having powerful items like this makes the role more attractive.
THE QUESTION
This leave me with a question, instead of nerfing these two items why not buff the others? Specifically, why are we not getting bigger buffs to shields and heals from items like
and
. This is a powerful stat that Riot has given supports but it remains woefully weakened. These items are absolutely terrible on Zyra, Velkoz, Malzahar, MF, and Brand yet champions like Lulu, Soraka, Janna, Nami and Karma often don't buy them for favor of
.
MY THEORY
My theory is to double (or at least add 10% to) the % shield and heal buff bonus on
and add 10-20% bonus to
. This might give incentives for players to play enchanter type supports and give them some serious late game strength to shields to survive against the very high burst of the Mages (and hopefully shift support mages to build AP more) in bot lane. This might lower the impact of Mages in the bot lane and bring real supports more strength hopefully making the support role more enticing for players at the same time. If this comes at the price that the % bonus shields and heals from items don't buff
and
or they have lower heal/shield to compensate all the better.
based on moving your allies across the map with speedboost from your passive, while giving meaning to your W active a 40% slow at max rank, scaling with ap, but who buys ap when your too busy building