I was about to suggest this - the real issue isn’t that it’s random, it’s that some of the manuals are completely Hit-or-Miss; you either get the 1 affix that helps you, or you get one of the 3-4 useless ones that dont.
If instead we had a manual for Frozen Orb which gave e.g. Cost Reduction, Size Increase, Chance to cast twice or ‘Insert useful Forb Affix here’ then you would rarely (if ever) feel like the item was changed from a potentially great upgrade to something way worse than what you have. It might not have the exact affix you would like, but at least it has something that helps.
Of course there would still always come a time when finding an upgrade becomes extremely unlikely. But right now you can have a 0GA item with the right affixes and tempers, find a 3GA with the right base affixes which then whiffs on both Tempers and is rendered worse than what you had. That would be unlikely or even impossible if you were at least guaranteed to get something that helps in some way.