I use pure feeds. I feed my Section D 'Fibre Balance'. He was always very sharp, spooky, anxious, bolshy. On this he has fantastic condition - his coat is always so shiny (everybody mentions it) and he is very calm to ride. It is quite expensive, but he only needs 1 kg per day and it gives him all his vits and mins. I don't add anything else. He loves it. I wouldn't use anything else.
My Andulucian x Freisan has only ever had pure balance alongside ad lib Haylage. He looks fantastic, has masses of energy (competes and hunts) and is mentally very well balanced. I find it a very economic feed. I reccomend it to all my clients who have Iberians or cobs as it seems to suit this type well. Easy to order and delivered within 48hours often next day.
I fed it when they first started (especially as they had 50% off ) but 3 out of my 6 horses reacted to it, gave them lumps and scurfy skin. They weren't very helpful either when I phoned them, so I haven't fed it since.
I did try it but found it quite expensive for feeding 7. 5 loved it but 2 not so keen. I had a grass analysis to find what vits and mins they needed and now use fast fibre as a base then progressive earths balancer with linseed and hi fibre nuts, works out much cheaper too.