Thank god for the quirky, randomness of procs, otherwise we'd probably all have matchy-matchy full sets in all our powers and all be doing the same thing. I don't disagree that some of the non damage procs like Numina, Prevent Med, etc can be confusing, but if they weren't, I suppose we wouldn't need a forum.
As others have said, losing set bonuses is a sacrifice to using procs. And procs are by no means an improvement to everything they're slotted in. It may take a bit of mids research and spreadsheet calculating to fine tune how to best leverage your goals with them, but I don't see that as a problem, I see it as part of the fun of this game.
A single AT can be played a myriad of ways and being able to slot it in a variety of ways for the way I intend to roll is a way to keep the toons from getting stale.
Further, while it may be silly to some, procs sometimes help me feel like they're adding nuance the story of my characters. For example, when my Earth Control/Savage Assault Dominator launches "Unkindness", that power is fully slotted with procs. With that, I think of each one of those ravens having their own purpose - %cold damage, %neg damage, %res debuff, %energy damage, %fire damage, and %smashing damage. I'm proud of those birds when all those orange numbers roll up. Sure, I could slot Unkindness with 6 Ragnaroks and get all those great set bonuses, but... yawn.